1 Introduction

The MAKO Robotic-Arm System was adopted within the past few decades and utilized today for total knee and total hip arthroplasties. This novel surgical technique was implemented into practice in order to cultivate a more controlled environment for physicians. By doing so, it facilitates the attainment of consistent surgical outcomes and avoiding technical imperfections engendered by a surgeon, such as malalignment and implant sizing.^1–3 This system may be particularly useful in patients with significant deformities and may help minimize incisions and postoperative pain.

Despite achieving good outcomes for a majority of patients through traditional surgical methods, the use of the MAKO Robotic-Arm System has continued to gain popularity for orthopedic surgeons, especially during total hip and total knee reconstructive procedures. This new and exciting innovation enables surgeons to create a virtual 3D model of the joint cavity through computerized tomography (CT) imaging.³ This information is then inputted into the MAKO software which builds a personalized surgical plan for each patient. During the procedure the system guides the surgeon and allows for further customization or modification of the plan as the surgery progresses. This ensures that proper sizing and alignment are accounted for, thus reducing intraoperative complication rates and potential human-error.^3,4

The literature has supported the use of the MAKO Robotic-Arm System for surgical candidates suffering from degenerative joint disease, but has not extensively reported surgical outcomes in an orthopedic oncology setting. Some of the most common orthopedic oncology disease processes that affect the joints include Pigmented Villonodular Synovitis (PVNS) and Chondromatosis. Radiation therapy has also shown to have a negative impact on the integrity of the bone and joint. Patients with impending pathological fractures may have concomitant degenerative joints due to arthritic conditions or secondary to radiation and/or treatments that can lead to avascular necrosis.

PVNS also called tenosynovial giant cell tumor diffusely affects the lining of joints and tendons. It commonly presents as a slow-growing neoplasm that causes inexplicable painless swelling in the affected joint. As the disease starts to progress, stiffness of the joint worsens and moderate to severe destruction of the joint occurs. This can eventually result in significant joint deformity, osteoarthritis and pain.

Chondromatosis is another type of uncommon benign tumor, which presents as small nodules of cartilage along the lining of joints, termed loose bodies. These nodules can then become loose and cause mechanical destruction resulting in swelling, pain, decreased range of motion, and sometimes locking of the joint. X-ray evaluation of the affected joint will typically reveal various sizes of the chondroid bodies and help guide clinicians with an appropriate diagnosis. In some instances, the chondroid lesions can ossify (turn into bone-like substance) and cause destruction of the cartilage lining the joints. This can eventually expose the surface of the joint, thus leading to significant joint deformity and osteoarthritis.

Patients with metastatic disease to their bone are commonly treated with radiation therapy in order to eradicate cancerous cells. Unfortunately, some research has shown, this type of intervention can potentially cause collateral damage to healthy tissue and bone as well. Specific bone complications include osteopenia, insufficiency fractures, bone necrosis as well as cartilage and joint degeneration.

The purpose of this study is to analyze the outcomes of patients who underwent a total hip arthroplasty (THA) or total knee arthroplasty (TKA) at Morristown Medical Center using the MAKO Robotic-Arm System. Specifically, we aimed to look at the use of the MAKO in an orthopedic oncology setting for patients with a degenerative hip or knee and a history of cancer or other orthopedic tumor, impending pathological fracture, PVNS, chondromatosis, radiation therapy, or other oncological related conditions.

2 Methods

A retrospective cohort study was conducted to identify orthopedic oncology patients that underwent MAKO robotic-assisted total hip and knee arthroplasty between September 2020 and November 2022 at a large, suburban, regional medical center. A retrospective chart review of the following was performed: patient demographics, body mass index (BMI), medications, hemoglobin, hematocrit, comorbidities, American Society of Anesthesiologists (ASA) Class, operative data, the length of stay (LOS), readmission rates due to infection or periprosthetic fractures, and complications. The inclusion criteria were orthopedic oncology patients with degenerative arthritis causing severe pain and difficulty performing daily living activities (ADLs) treated at our facility using the MAKO Robotic-Arm System. Exclusion criteria included revision arthroplasty patients and total primary knee or hip replacements without the use of the MAKO Robotic-Arm System. All confidence intervals were calculated at the 95% confidence level. Demographics such as gender, age, body mass index (BMI), American Society of Anesthesiologists Score (ASA), and LOS (length of stay) were included in our analysis. Medical comorbidities such as congestive heart failure (CHF), hypertension, peripheral vascular disease (PVD), cerebrovascular disease, dementia, chronic obstructive pulmonary disease (COPD), diabetes mellitus, chronic kidney disease (CKD), liver disease, AIDS, hypertension, anxiety or depression, osteoporosis, obstructive sleep apnea (OSA), high cholesterol, and coronary artery disease (CAD) were also identified for each cohort.

3 Results

We identified 25 patients that underwent MAKO robotic-assisted total hip and knee arthroplasty between September 2020 and November 2022. The average age of the patients was 66.04 years old with the youngest being 50 years old and the oldest being 79 years old. Of the patients in our population, 72% (18/25) were Caucasian, 12% (3/25) were Asian or Indian, 8% (2/25) were African American and 8% (2/25) did not identify with an ethnicity. The average BMI was 29.7. Regarding the operative site, 52% (13/25) of the operations were performed on knees and 48% (12/25) were on hips. Specifically, 54% (7/13) of the TKAs were of the left knee and 46% (6/13) were of the right knee. Of the THAs, 50% were performed on each of the right and left hips. In our study, 4 patients had prostate cancer, 3 patients had synovial chondromatosis, 2 patients had multiple myeloma, 2 patients had breast cancer, 2 patients had subchondral cyst formation, and 2 patients had benign masses of the femur, yet each other patient had a unique orthopedic oncology condition. These included: kaposi sarcoma, metastatic vulvar cancer, avascular necrosis from previous radiation to the area secondary to metastatic prostate cancer, low grade liposarcoma, thyroid cancer, lymphoma, lipoma arborescens, pigmented villonodular synovitis, previous radiation to the area secondary from a high grade pleomorphic sarcoma, radiation to the area secondary to spindle cell sarcoma, metastatic lymphoma and avascular necrosis, bladder cancer, metastatic lung cancer, leukemia, and an amputation secondary to HIV and squamous cell carcinoma. Additionally, the surgical indication in 92% (23/25) was osteoarthritis, 4% (1/25) was avascular necrosis and 4% (1/25) was hip dysplasia as seen in Table 1. Of the 36% (9/25) of patients with metastatic disease to the bone, 44% (4/9) had impending pathological fractures. Additionally, all patients with either PVNS or Synovial Chondromatosis (4/25) simultaneously underwent an arthroplasty and synovectomy to remove the benign condition.

Of the patient population, 60% (15/25) of patients had hypertension, 56% (14/25) of patients had high cholesterol, 24% (6/25) of patients had anxiety or depression, 20% (5/25) of patients had coronary artery disease, 12% (3/25) of patients had diabetes mellitus, 12% (3/25) of patients had obstructive sleep apnea, 4% (1/25) of patients had congestive heart failure, 4% (1/25) of patients had peripheral vascular disease, 4% (1/25) patient had cirrhosis, and 4% (1/25) patient had HIV. No patients had cerebrovascular accidents, dementia, COPD, chronic kidney disease, or osteoporosis as seen in Table 2.

Regarding the operation, the average ASA score of TKA and THA patients was 2.31 and 2.33 respectively, and the average length of the surgery was 2 h and 41 min and 2 h and 33 min, respectively. In the operation 64% (TKA - 7, THA- 9, 16/25) of patients had general anesthesia, 24% (TKA- 6, THA- 0, 6/25) of patients had spinal regional anesthesia, and 12% (TKA- 0, THA- 3, 3/25) of patients had spinal and general anesthesia.

The average preoperative hematocrit and hemoglobin for TKA patients was 42.3 ± 2.4% and 13.6 ± 0.7 g/dL respectively, whereas the postoperative hematocrit and hemoglobin was 35.4 ± 2.1% and 11.4 ± 0.7 g/dL, respectively. The average preoperative hematocrit and hemoglobin for THA patients was 36.2 ± 5.0% and 12.1 ± 1.6 g/dL respectively, whereas the average postoperative hematocrit and hemoglobin 30.8 ± 4.2% and 10.2 ± 1.3 g/dL respectively. The estimated blood loss during the operation for THA and TKA patients was 261 ± 162 mL and 292 ± 235 mL, respectively. A tourniquet was used for all TKA procedures. The average length of stay postoperatively for TKA and THA patients was 2.6 days and 3.9 days, respectively.

For all operations, the average preoperative hematocrit was 39.4 ± 2.8% and the average preoperative hemoglobin was 12.9 ± 0.9 g/dL, whereas the average postoperative hematocrit and hemoglobin was 33.2 ± 2.3% and 10.8 ± 0.7 g/dL, respectively. The estimated average blood loss during each of the 25 operations was found to be 222 ± 124 mL. The average length of stay postoperatively was 3.2 days, and there were no complications during any of the procedures as seen in Table 3.

In the postoperative period, patients were followed for an average of 16.32 months. Readmission and complication rates were counted at the 1–30, 1–60, 1–90, and 1-year marks. There were no readmissions at any of our recorded intervals as seen in Table 4, but one patient did present to the emergency department after falling 4 days post-operatively. X-ray imaging revealed no malalignment of the prosthesis or periprosthetic fracture. Additionally, one patient experienced an intraoperative fracture, however it was not attributable to the use of the MAKO Robotic-Arm System.

4 Discussion

Within the existing literature, there is but a single study delving into the use of the MAKO Robotic-Arm System in the management of orthopedic oncology conditions. Specifically, a case report regarding a patient who underwent MAKO-assisted hip arthroplasty due to metastatic renal cell carcinoma of the acetabulum.⁵ To our knowledge, however, this is the only case series reported in the literature on the use of the MAKO System in an orthopedic oncology setting for patients undergoing a total hip or total knee arthroplasty.

It's worth noting that the MAKO Robotic-Arm System was only implemented into practice a few decades ago, but has continued to gain popularity over the years. Sloan et al. performed a retrospective review using the National Inpatient Sample and reported that primary total hip arthroplasty (THA) is expected to grow 71%, to 635,000 procedures, and primary total knee arthroplasty is projected to grow 85%, to 1.26 million procedures by 2030.⁶ Additionally, Wilson et al. predict that the cost of total joint arthroplasty (TJA) procedures will rise from $5 billion in 2006 to $50 billion by 2030.⁷ With the total volume of total joint arthroplasty surgeries continuing to increase, it is expected that the number of complications will follow. As hospital systems continue to transition towards a bundled payment model it becomes imperative to reduce readmission rates and total joint complications in order to manage the costs of care. Robotic surgery for joint replacement may have the potential for improving outcomes and minimizing complications especially for patients with more complex conditions and/or deformities that may predispose them to higher complication rates.

When evaluating the cost-effectiveness of this procedure versus the manual technique, it is imperative to account for the cost of the robot, which has been reported to be as high as $1.5 million. However, studies have reported that when the total cost of care is accounted for and a Markov decision analysis is performed, the robotic system is more cost effective when the number of surgeries exceeds 94 annually, failure rates are less than 1.2% at 2 years, and patient age is taken into consideration.⁴ Rajan et al. also performed a Markov Model-Based Evaluation on the cost-effectiveness of robotic surgery versus manual surgery in total knee arthroplasty procedures. It was concluded from their analysis that the robotic assisted surgeries offered lower annualized revision rates and superior postoperative outcomes when compared to manual procedures, especially when case volume exceeded 24 surgeries per year.⁸ Interestingly though, Karunaratne et al. conducted a systematic review and meta-analysis analyzing the effectiveness of robotic hip and knee surgery on patient reported outcomes and concluded patient satisfaction for those who underwent an active robot arm-assisted THA or TKA was comparable with conventional surgery.⁹ Regardless, future prospective clinical investigation is still required in order to substantiate that robotic assisted total joint procedures offer overall superior cost-effective outcomes than the manual technique.

Total joint arthroplasty, specifically, total hip and total knee arthroplasty, is one of the most successful orthopedic surgeries due to 90% long-term survivorship at 15 years.^1,2 Concurrently, the use of robotics is emerging as a new technology for the management of hip and knee arthroplasties.³ Although the first robotic system for an orthopedic procedure was developed at the University of California - Davis from 1986 to 1992, the use of robotics in orthopedics, is still in its infancy. Current features include robotic arm-assisted, robotic guided cutting jigs, and robotic milling systems using active, semi-active or passive control systems.⁴ Current perceptions of why orthopedic surgeons intend to use the robotics for operations include improvements in joint alignment.^10,11 Specifically, Sherman and Wu conducted a study to examine the utilization, motivations and perceptions of total joint surgeons using robotics by sending a survey to all members of the American Association of Hip and Knee Surgeon. It was concluded that increased precision was a primary motivator along with nonclinical motivators such as marketing, administrative pressure, and peer pressure.¹² Additionally, they stated the draw of potential financial benefits may be particularly important for hospitals and surgeons in saturated regions, where the use of novel technology can be a factor for remaining viable in a competitive market.¹²

The use of the MAKO Robotic-Arm System has been implemented into practice by orthopedic surgeons across a broad setting. Currently, the robotic assisted system has been used for spinal fusion and instrumentation procedures as it may aid with intraoperative navigation, trajectory determination, and screw implantation.¹³ Specifically, many studies have shown robotic-assisted spine surgery demonstrates screw placement accuracy is superior to that of free-hand screw placement.^14–16 Additionally, robotic surgery has been used in orthopedic trauma cases with positive outcomes. Operations have been performed on the femur, pelvis and hand,^17–20 thus, this phenomenon may explain increased usage of robotics in orthopedic trauma in the future. Further, though not robotics, Hua et al., Eichhorn, and Angelini et al. showed that computer-assisted navigation systems can not only improve the accuracy of ACL reconstruction tunnels but also reduce the learning curve of novice surgeons.^21–23 Likewise, robotic surgery has been accepted in the fields of general surgery, neurosurgery and urology for two decades.²⁴

In our study, we assessed the efficacy of this procedure in an orthopedic oncology setting by a single surgeon. To our knowledge, this is the first case series reported in the literature analyzing the outcomes of its use in an orthopedic oncology setting. In the timeframe of this study period, all orthopedic oncology patients that underwent a total hip or knee arthroplasty were surgically treated with use of the MAKO Robotic-Arm System rather than the manual technique. Due to the ability of the MAKO Robotic-Arm System to offer increased precision and radiographic improvements in joint alignment, it was determined in our patient cohort that this technique would provide more optimal surgical outcomes, especially for a patient population with more complicated surgeries due to compromised bone and joint quality and deformity in some cases. Many oncological conditions and treatments affect the quality of bone and joints, and with a growing population it is expected the number of cases will subsequently increase. In our study, patients presented with a variety of oncological conditions (Table 1), but the most common disease processes that affect the joints in our population include Pigmented Villonodular Synovitis (PVNS), Chondromatosis, and Metastatic Disease. Radiation therapy has also been shown to have a negative impact on the integrity of the bone and joint.

Annually, the incidence rate of PVNS is roughly 1.8 per million in the worldwide population. PVNS is slow growing, and patients will typically complain of painless swelling during the early stages of the disease process. Microscopic analysis of PVNS reveals mononuclear cells, macrophages with hemosiderin-stores, and multinucleated osteoclast-type giant cells. The median time of a definitive diagnosis has been reported as high as 18 months, with most cases presenting in the knee joint.²⁴ As the tumor begins to expand in size, patients will experience reduced range of motion. Recurrent bleeding within the joint results from advanced stages of PVNS and can cause severe stiffness and joint destruction. PVNS can present as diffuse which involves the entire synovial tissues and cause more prominent symptoms of swelling and pain versus localized PVNS which is less destructive to the joint and has a lower rate of recurrence. MRI imaging is the optimal diagnostic tool for clinicians to detect PVNS in its early stages.²⁵ Once the disease process has advanced, patients are at risk for significant joint deformity and osteoarthritis. In advanced stages of disease with secondary osteoarthritis, a total joint arthroplasty procedure can be implemented as a viable treatment option. Hamlin et al. was one of the first studies to report positive outcomes in patients who underwent a TKA for the treatment of PVNS with secondary osteoarthritis, and recent systematic reviews support this claim.^26,27

Chondromatosis affects roughly 1 per 100,000 people. In its early stages synovial chondromatosis will present as sessile cartilaginous foci in synovial membranes, tendon sheaths, and bursae. Patients will typically present with pain, swelling, and occasional mechanical “locking.” As the disease progresses, the lesions grow and detach from the synovium and become free. These “loose bodies” will continue to grow and about two-thirds will ossify through endochondral ossification. This can result in more prominent symptoms of pain and swelling of the joint. MRI imaging should be used to determine the extent of the disease. In its more advanced stages, the loose bodies can cause mechanical damages to the articular surfaces and result in significant joint deformity and osteoarthritis. In cases refractory to conservative treatment, a total joint arthroplasty procedure has successfully been performed for the treatment of patients with synovial chondromatosis and osteoarthritis.²⁸

Metastatic cancer is one of the most common disease processes that affects the bone. In particular, up to 70% of patients with either breast or prostate cancer experience metastatic disease to the extremities. The shoulder, hip, and knee joints are common sites for metastatic disease. Impending pathological fractures in these anatomical regions have successfully been treated with a hemi or total joint arthroplasty procedure using the manual technique, but the literature has not reported outcomes on the use of robotic assisted technique. Additionally, radiation therapy is common among this patient population, and has shown to impact the quality of the joint. Specific bone complications resulting from exposure to radiation therapy include osteonecrosis, osteopenia, insufficiency fracture, growth arrest, and malignancy.²⁹ Articular cartilage is typically considered radio-insensitive, and thus does not leave patients undergoing radiotherapy for metastatic disease prone to developing osteoarthritis. However, there have been inconsistencies in the literature as to whether or not radiation therapy has deleterious effects on articular surfaces. Hong et al. reported cellular senescence in articular cartilage exposed to gamma radiation at a dose rate of 3.81 Gy/min.³⁰ However, additional studies have demonstrated active degradation of articular cartilage exposed to 2Gy gamma radiation^31,32 and with 3Gy–7Gy of X-ray radiation.³³ With radiation therapy being an integral part of care for patients with metastatic disease it is imperative future studies continue to analyze any adverse effects on patients that would predispose or put them at risk for developing significant joint deformity and osteoarthritis.

As further clinical investigation continues on the comparative efficacy of the MAKO Robotic-Arm System and the conventional manual surgical technique, our case study strongly advocates for its use within the realm of orthopedic oncology. This advanced system provides a safe and reliable surgical option in this select patient population, who may have more complex and complicated conditions that may also require combined surgeries such as concomitant tumor removal and synovectomies. Although one patient experienced an intraoperative fracture following malleting a stem component into the bone, this was unrelated to the use of the MAKO Robotic-Arm System. Furthermore, this patient subsequently underwent fixation with a Stryker plate, screws, and cables. Post-operatively, no complications were reported in our study population. Patients who underwent palliative treatment for metastatic disease reported significant relief of pain as well as restorative function of the afflicted joint. Additionally, since zero patients were readmitted, all patients were pain free at 6 weeks with range of motion restored in the afflicted joint. When compared to studies documenting average metrics for patients undergoing total joint arthroplasty via the manual technique, our findings revealed comparable results in terms of length of stay,³⁴ total blood loss,^35,36 and surgical time.³⁷ Consequently, we can safely advocate for its use in selected patients and conclude the MAKO does not adversely affect patient outcomes.

Although the MAKO is considered a more novel and innovative technique for orthopedic surgeons, Sodhi et al. have reported on the learning curve associated with its use versus the traditional manual technique. Their study analysis concluded that within a few months, a board-certified orthopedic surgeon should be able to adequately perform robotic surgery without adding operative times.³⁸

In our population, we did not make any modifications to the standard MAKO approach, as the purpose of this paper was to show that the standard approach was safe and reliable even considering the oncological history of these patients. Many of whom required an additional portion of the operation such as tumor resection or extensive synovectomy. It was not, however, written to indicate how the utilization of the MAKO system can be altered to consider the poor bone quality or additional comorbidities typically found in orthopedic oncology patients.

There were several limitations included in our study. As a retrospective review of patient records, it includes all inherent biases associated with retrospective studies. We also had a small patient cohort, which was due to our hospital system only recently introducing the MAKO into practice within the past two years. Additionally, there was not a side-by-side comparison of surgical outcomes on the manual technique included. This limits our ability to conclude that the MAKO Robotic-Arm System is more efficacious than the manual technique. Nevertheless, zero patients were readmitted, all patients were pain free at 6 weeks with range of motion restored in the afflicted joint, and LOS,³⁴ total blood loss,^35,36 and surgical time³⁷ were not significantly more than studies reporting on manual technique averages for patients undergoing a total joint arthroplasty. Thus, we can advocate for its use and conclude that the MAKO does not significantly compromise patient outcomes. This is the only case series reported in the literature on the use of the MAKO in an orthopedic oncology setting though and outcomes may vary in other hospital systems since surgeries were performed by a single surgeon.

Along with these limitations, in our context, the application of the MAKO Robotic-Arm System was directed towards addressing the sequelae resulting from orthopedic oncology issues, such as osteoarthritis, avascular necrosis, and hip dysplasia. Consequently, our study neglected to include a cohort of patients where the MAKO Robot was used to treat direct orthopedic oncology conditions (i.e. tumor resection, tumor navigation, or precision surgical intervention). A single study utilizing the MAKO System for tumor resection has been published, advocating for its improved accuracy over manual techniques.³⁹ However, this was a pilot study and was simulated using distal femur Sawbone models rather than being implemented in real clinical scenarios.

A prospective randomized controlled trial with multiple surgeons and a larger patient population should be performed in order to provide more external validity. Specifically, aiming to further substantiate the superior outcomes offered by the MAKO System compared to manual techniques for patients undergoing total hip or knee arthroplasty within an orthopedic oncology context. We furthermore encourage future research to investigate the efficacy of the MAKO Robotic-Arm System in cases where orthopedic oncology conditions are the primary surgical indication. This would provide sarcoma surgeons with subspecialty-specific education in the use of this novel robotic arm system.

5 Conclusion

Although still in its infancy, the MAKO Robotic-Arm System may offer promising implications for its use over the traditional manual technique in selected orthopedic oncology patients undergoing a total joint arthroplasty. This population is considered a more compromised patient cohort and can result in a more complicated surgery with more risks. The results of this study demonstrate that its use in an orthopedic oncology setting in selected patients can be safe and provide optimal outcomes for patients. It was especially helpful in pre-operative planning for patients with significant joint deformities. However, its role within the field will be further defined in the upcoming years as it continues to gain popularity and be applied more broadly by orthopedic oncology surgeons. Future clinical investigation and prospective research should be performed in order to support the use of the MAKO over traditional manual techniques.

Consent

All patients included in the study signed consent allowing us to access their medical and surgical history for future investigation.

Ethical statement

1)This material is the each of the authors own original work, which has not been previously published elsewhere.2)The paper is not currently being considered for publication elsewhere.3)The paper reflects the authors own research and analysis in a truthful and complete manner.4)The paper properly credits the meaningful contributions of co-authors and co-researchers.5)The results are appropriately placed in the context of prior and existing research.6)All sources used are properly disclosed and correctly cited.7)All authors have been personally and actively involved in substantial work leading to the paper, and will take public responsibility for its content.8)All patients included in the study signed consent allowing us to access their medical and surgical history for future investigation.9)All patients included in the study were deidentified and given a respective number, as to comply with HIPAA regulations.

Funding statement

We did not receive any funding for this study by any grant or trust.

Declarations of interest

None.

No funding was received for this research project.

Patient consent was obtained through the IRB.

CRediT authorship contribution statement

Tyler Hoskins: Investigation, Supervision, Writing – original draft. Brian Begley: Writing – original draft, Investigation. Joseph D. Giacalone: Writing – original draft, Writing – review & editing, Investigation. Kristen De Wilde: Formal analysis, Writing – original draft. Francis Maguire: Data curation. James Wittig: Supervision, Validation, Writing – review & editing.