This article is more than 5 years old. Information may no longer be current.

Accuracy of Implant Alignment and Early Results After Minimally Invasive vs Conventional OrthoPilot-navigated Columbus TKA

Add topic to email alerts

Receive an email when new articles are posted on

Please provide your email address to receive an email when new articles are posted on .

Subscribe

Added to email alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

Back to Healio

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Back to Healio

Abstract

The goal of this study was to evaluate potential risks and benefits of minimally invasive vs conventional approaches in navigated total knee arthroplasty (TKA) in 50 patients. Preoperatively, no statistically significant differences between the two groups were found for deformity, range of motion (ROM), clinical scores, and ligament stability in the native joint or after prosthesis implantation measurements intraoperatively. Postoperatively, there were no significant differences between the two groups for deformity and clinical scores. In contrast, significantly less pain according to VAS measures and quicker improvements in ROM during the first 10 postoperative days were experienced in the minimally invasive group. Complication rates were similar in both groups. According to our results, minimally invasive navigated TKA is characterized by high implant positioning accuracy, soft tissue management quality, and complication rates similar to those for conventional approaches. Compared with the conventional approach, minimally invasive TKA provides superior functional results and less pain in the early postoperative period.

Since the 1970s, total knee arthroplasty (TKA) has evolved as a reliable and successful procedure in the treatment of degenerative knee joint diseases. There is a discrepancy, however, between the surgeon’s definition of success, which emphasizes long-term implant performance and low revision rates, and the patient’s treatment goals, which emphasize rapid and painless return to function early in the postoperative period.¹ The new minimally invasive approach in TKA may be the procedure that meets both patient and surgeon expectations.

There is ongoing discussion about the potential benefits of minimally invasive techniques in total joint replacement, such as less pain, faster functional recovery, less blood loss, and shorter hospitalization. There are also increased risks, such as malalignments and fixation errors, insufficient soft tissue management, and generally higher complication rates.^2,3 Navigation systems were shown to increase precision and reliability in implant alignment in several studies.^4-8 In minimally invasive surgery navigation systems may help reduce errors caused by limited view of the surgical field, although there is insufficient scientific evidence for this in the literature.

Our study evaluated potential risks and benefits of minimally invasive vs conventional approaches in navigated TKA.

Materials and Methods

Of the 50 procedures in 50 patients included in this study, 25 were treated using a conventional medial parapatellar (CMP) approach and 25 were treated using a mini-midvastus split (MMS). In the MMS approach, a skin incision is made along the medial border of the patella, extending from slightly above the superior pole of the patella to the upper margin of the tibial tuberosity. The medial patellar retinaculum is dissected. From the superior pole of the patella, an oblique vastus split of 1.5-2 cm is made along the muscle fibers. The suprapatellar pouch is preserved. The patella is not everted but subluxated laterally. Figure 1, A and B, illustrates the MMS approach used in this study.

Exclusion criteria for the minimally invasive technique were applied to both groups. These included body mass index (BMI) >40 kg/m², varus or valgus deformity >20°, flexion contracture >20°, range of motion (ROM) <60°, rheumatoid arthritis, steroid medication, diabetes, and significant osteoporosis.

Demographic data for all patients are shown in the Table. There were no statistically significant differences preoperatively between the two groups except for a slightly lower BMI (25±5 vs 31±5; P<.01) in the MMS group.

All TKAs were performed by one surgeon using the Columbus CR knee system supported by the OrthoPilot TKA 4.2 navigation system (both by B. Braun Aesculap, Tuttlingen, Germany). In all patients, the posterior cruciate ligament (PCL) was preserved, the patella was not resected, and all components were cemented. Postoperatively, patients underwent standardized rehabilitation procedures, which included mobilization during the first postoperative day with initial full weight bearing, daily continuous passive motion (CPM), and daily physiotherapy.

Pain management, including systemic analgesia (basic medication with non steroidal antiinflammatory drugs [NSAID], ibuprofen 1200 mg per day), metamizol (2000 mg per day), and a peridural pain catheter with a mobile pump for self-medication (200 mL 2% ropivacain, 100 µg sulfentanyl) was identical in the two groups. Catheterization was implemented from the day of surgery until postoperative day 5.

Preoperatively, the Knee Society Score (KSS function and knee score), the Oxford score, clinical passive ROM, and the radiologic deformity (mechanical leg axis on long-leg-standing radiography) were documented in both groups. Intraoperatively, deformity (mechanical leg axis in full extension), ROM (passive motion between maximal extension and flexion), and ligament stability (axis deviation under maximal manual varus or valgus stress in 15° of flexion) were evaluated for the native joint using the navigation system as a measuring tool. In a second procedure, which was performed after the final implantation of the original components, the navigation system was restarted, and all kinematic and anatomic data were remeasured. Deformity, ROM, and stability were reevaluated by navigation for the implanted prosthesis. Thus, both the pathologic conditions in the degenerated native knee joint and their correction by implant could be documented intraoperatively by navigation. Postoperatively, clinical ROM and pain (according to VAS measures) were evaluated from day 1 to day 10. On postoperative day 7, deformity was again determined radiologically. Between 3 and 6 months postoperatively, KSS and Oxford scores for each group were reevaluated.

Statistical analysis of the data was performed using the Student t test.

Results

Deformity Measured Radiologically

Deformity was measured radiologically pre- and postoperatively. Preoperatively, deformity was 10º±5º (range, 3º-18°) in the MMS group and 9°±5° (range, 1°-17°) in the CMP group. Postoperatively, deformity was corrected to 2°±1° (range, 0°-4°) in the MMS group and 1°±1° (range, 0°-5°) in the CMP group. There were no statistically significant differences with regard to radiologic deformity between groups, either pre- or postoperatively.

Deformity Measured by Navigation

Deformity was also measured intraoperatively by navigation. In the native knee joint, deformity was 7°±3° (range, 3°-16°) in the MMS group and 6°±3° (range, 1°-16°) in the CMP group. After the final implantation of the prosthesis, deformity was corrected to 1°±1° (range, 0°-3°) in the MMS group and 2°±1° (range, 0°-5°) in the CMP group. Again, there were no statistically significant differences in deformity measured intraoperatively by navigation between groups, either in the native knee joint or with the implant.

ROM Measured Clinically and by Navigation

Preoperatively, clinical ROM was 106°±21° (range, 60°-130°) in the MMS group and 112°±12° (range, 90°-130°) in the CMP group. Intraoperatively, passive ROM was also measured by navigation. In the native knee joint, the navigated ROM was 134°±10° (range, 118°-153°) in the MMS group and 132°±11° (range, 106°-151°) in the CMP group. After the final implantation of the prosthesis, the navigated ROM was 143°±8° (range, 125°-153°) in the MMS group and 140°±8° (range, 125°-150°) in the CMP group.

No statistically significant differences were found for passive ROM measured clinically and by navigation between the two groups, either pre- or intraoperatively.

Stability Measured by Navigation

The data in Figure 2 are normalized to the present varus or valgus deformity in each patient and indicate the leg axis deviation under maximal varus and valgus stress in 15° of flexion measured by navigation. Both groups showed stable and well balanced ligamentous results after implantation of the prosthesis. For the native knee joint and after the final implantation of the prosthesis, there were no statistically significant differences between the two groups.

Postoperative ROM Measured Clinically

There was a statistically significant continuous improvement in ROM after surgery (P<.05) during the first 10 postoperative days in both groups (Figure 3). Except on postoperative day 4, however, the daily gain in ROM was significantly greater in the MMS group compared with the CMP group (P<.05).

Pain Measured by VAS

There was a statistically significant continuous reduction in pain (P<.05) measured by VAS during the first 10 postoperative days in both groups (Figure 4). Patients in the MMS group reported significantly less pain during the first 10 postoperative days compared with patients in the CMP group according to VAS measurements (P<.05).

KSS Function Score, KSS Knee Score, and Oxford Score

Preoperatively, KSS function score was 50±17 (range, 5-70) in the MMS group and 58±11 (range, 40-70) in the CMP group. KSS knee score was 26±12 (range, 0-45) in the MMS group and 31±11 (range, 16-49) in the CMP group. The Oxford score was 41±4 (range, 31-46) in the MMS group and 38±2 (range, 35-41) in the CMP group. Neither group showed statistically significant differences in preoperative scores.

At the postoperative follow–up, which was performed 3 to 6 months after implantation, all scores improved significantly (P<.05). KSS function score was 82±14 (range, 50-100) in the MMS group and 81±20 (range, 50-100) in the CMP group. KSS knee score was 81±17 (range, 51-100) in the MMS group and 78±15 (range, 46-91) in the CMP group. The Oxford score was 23±8 (range, 12-38) in the MMS group and 24±11 (range, 16-46) in the CMP group. At follow-up, neither group showed statistically significant differences in postoperative scores.

Blood Loss, Surgical Time, and Length of Incision

Blood loss was comparable between the groups, with an average of 410±208 mL (range, 100-840 mL) in the MMS group and 574±319 mL (range, 290-1500 mL) in the CMP group (not significant). Surgical time was significantly longer in the MMS group (P<.05), measuring 74±9 min (range, 55-85 min) compared with 63±14 min (range, 45-80 min) in the CMP group. Length of skin incision was significantly shorter in the MMS group (P<.001), measuring 11±1 cm (range, 9-14 cm) compared with 18±2 cm (range, 15-21 cm) in the CMP group.

Complications

One minor femoral notching (less than the thickness of the saw blade) occurred in each group. There was one uncomplicated revision for hematoma in the CMP group and one uncomplicated deep vein thrombosis in the CMP group. There were no wound-healing or septic complications in either group.

Discussion

There is debate on minimally invasive procedures in total joint replacement not only in the medical community, but also among patients, in the industry, and in the media. In this study, the potential risks and benefits of minimally invasive and conventional approaches in navigated TKA were compared.

There were some limitations, however, to interpreting the results of this evaluation. The number of patients was relatively small, and only very early results could be analyzed. Furthermore, patients were not statistically randomized, although the study was prospective and, because of identical patient exclusion criteria, preoperative patient data were comparable between the CMP and MMS groups. Applying the same exclusion criteria to both groups would theoretically avoid a bias toward treatment of more severe cases in the CMP group; these cases would have been unsuitable for the minimally invasive approach.

Critics of minimally invasive surgery in total joint replacement suggest that increased complication rates are due to limited view of the anatomic field during surgery.³ We could not find any significant differences in quality of implant alignment and soft tissue balancing or in general complication rates between the MMS and CMP groups in our study. This may indicate that if patients had been grouped according to the appropriate surgical approach, with appropriate contraindications applied, and a navigation system used to help determine correct component alignment and soft tissue balancing despite limited surgical view, complication rates would not have been higher in the MMS group. Furthermore, because performing TKA involves a significant learning curve, the procedure should be performed only by an experienced surgeon. Finally, the data presented here do not address the risks of minimally invasive approaches in TKA if a navigation system is not used to compensate for the limited surgical view.

The benefits of minimally invasive TKA shown in the MMS group were significantly less pain according to VAS measures and a quicker gain of function during the first 10 postoperative days. There were no significant clinical differences between the two groups, however, according to KSS and Oxford scores at the 3- to 6-month follow-up.

Our results are consistent with most findings in the literature. In a retrospective matched-pairs analysis, Haas et al⁹ compared the results of minimally invasive vs conventional nonnavigated TKA. They showed improved ROM at the 6-week, 12-week, and 1-year follow-up in knees that underwent minimally invasive surgery. In contrast to our findings, these researchers noted better KSS scores at the 1-year follow-up for knees that underwent minimally invasive TKAs. They did not find differences in implant alignment or complication rates between the groups in their study. In a prospective study by Laskin et al,¹⁰ patients experienced improved ROM and had less pain during the first 6 postoperative days and after 6 weeks. In addition, KSS scores were better at 6 weeks postoperatively in the knees that underwent minimally invasive surgery. At 12 weeks postoperatively, no significant differences were found in ROM, KSS scores, or VAS measures. No differences in the quality of implant alignment were found. In a prospective, randomized study, Hart et al¹¹ compared minimally invasive navigated and conventional nonnavigated TKA. During the first 10 postoperative days, ROM, KSS, and VAS measures were better in minimally invasive TKA; however, after 6 and 12 weeks, no significant differences were observed. The researchers found no differences in implant alignment, blood loss, or intra- and postoperative complications, although minimally invasive procedures took longer. Seon et al¹² conducted a prospective, randomized trial to compare knees that underwent minimally invasive navigated and conventional nonnavigated surgery. ROM was greater up to 1 week postoperatively, pain was less up to the 3 days postoperatively, and blood loss was lower in the minimally invasive group, although complication rates were similar in both groups. Two weeks postoperatively, there were no significant differences in ROM and VAS, and there were no differences in implant alignment and surgical time between the groups.

According to the literature and our results, minimally invasive TKA compared with the conventional procedure produces accurate implant positioning, soft tissue balancing, and comparable complication rates, especially if a navigation system is used to compensate for the limited view of the anatomic field. Functional results are superior, and there is less pain in the very early postoperative period, which we defined as the first 10 days postoperatively, compared with results after the conventional approach. The clinical relevance of these findings and their impact on long and mid-term results are not yet clear. Additional research is necessary to fully evaluate potential benefits of minimally invasive TKA, especially in the mid and long term.

References

1. Trousdale RT, McGrory BJ, Berry DJ, Becker MW, Harmsen WS. Patients’ concerns prior to undergoing total hip and total knee arthroplasty. Mayo Clin Proc. 1999; 74(10):978-982.
2. Laskin RS. New techniques and concepts in total knee replacement. Clin Orthop Relat Res. 2003; (416):151-153.
3. Hungerford DS. Minimally invasive total hip arthroplasty. In opposition. J Arthroplasty. 2004; 19 (4 suppl 1):81-82.
4. Bäthis H, Shafizadeh S, Paffrath T, Simanski C, Grifka J, Luring C. Are computer assisted total knee replacements more accurately placed? A meta-analysis of comparative studies. Orthopäde. 2006; 35(10):1056-1065.
5. Chin PL, Yang KY, Yeo SJ, Lo NN. Randomized control trial comparing radiographic total knee arthroplasty implant placement using computer navigation versus conventional technique. J Arthroplasty. 2005; 20(5):618-626.
6. Decking R, Markmann Y, Fuchs J, Puhl W, Schorf HP. Leg axis after computer navigated total knee arthroplasty: a prospective randomized trial comparing computer navigated and manual implantation. J Arthroplasty. 2005; 20(3):282-288.
7. Ensini A, Catani F, Leardini A, Romagnoli M, Granni S. Alignments and clinical results in conventional and navigated total knee arthroplasty. Clin Orthop Relat Res. 2007 Apr; 457:165-162.
8. Bäthis H, Shafizadeh S, Paffrath T, Simanshi C, Grifka J, Luring C. Are computer assisted total knee replacements more accurately placed? A meta analysis of comparative studies. Orthopaede. 2006; 35(10):1056-1065.
9. Haas SB, Cook S, Beksac B. Minimally invasive total knee replacement through a mini-midvastus approach: a comparative study. Clin Orthop Relat Res. 2004 Nov; (428):68-73.
10. Laskin RS, Beksac B, Phongjunakorn A, et al. Minimally invasive total knee replacement through a mini-midvastus incision: an outcome study. Clin Orthop Relat Res. 2004 Nov; (428):74-81.
11. Hart R, Janecek M, Cizmar I, Stipcak V, Kucera B, Filan P. Minimally invasive and navigated implantation for total knee arthroplasty: X-ray analysis and early clinical results [in German]. Orthopäde. 2006; 35(5):552-557.
12. Seon JK, Song EK. Navigation-assisted less invasive total knee arthroplasty compared with conventional total knee arthroplasty: a randomized prospective trial. J Arthroplasty. 2006; 21(6):777-782.

Authors

Drs Lampe, Bohlen, Dries, Sufi-Siavach, and Hille are from the Department of Orthopaedics and Traumatology, Joint Replacement Center, Klinikum Eilbek – Schoen Kliniken, Hamburg, Germany.

Correspondence should be addressed to: Karina Bohlen, Klinikum Eilbek – Schoen Kliniken, Dehnhaide 120, D-22081 Hamburg, Germany.

This study was supported by B. Braun Aesculap, Tuttlingen, Germany.

Drs Lampe, Sufi-Siavach and Bohlen are members of the B. Braun Aesculap speaker’s bureau. Drs Dries and Hille have no financial relationships to disclose.