The aim of this study was to compare the results in patients having a quadriceps sparing total knee replacement (TKR) with those undergoing a standard TKR at a minimum follow-up of two years.
All patients who had a TKR with a high-flex posterior-stabilised prosthesis prior to December 2002 were reviewed retrospectively. There were 57 patients available for follow-up. Those with a quadriceps sparing TKR had less pain peri-operatively with a greater degree of flexion at all the post-operative visits and at the final follow-up, but their operations took longer, with less accurate radiological alignment. There was no difference in the complications and in the Knee Society scores between the two groups at the final follow-up.
Total knee replacement through a quadriceps sparing approach has some peri-operative advantages over the standard incision. At a minimum follow-up of two years the clinical results were similar to those with a standard incision, but the radiological outcomes of the quadriceps sparing group were inferior.
Total knee replacement (TKR) through a standard incision produces good long-term results.1–7 Balancing the ligaments and achieving the correct alignment are paramount in eliminating premature failure.8 An extensile exposure with clear visibility of the entire joint is imperative in achieving excellent long-term results.
However, in spite of the good results achieved with a standard TKR, there is currently a trend towards limiting the operative exposure in order to decrease the morbidity related to the operation. Limited incisions lead to a decrease in visualisation of the operative field which may compromise the long-term results. There is some evidence to suggest that minimally-invasive surgery does decrease the morbidity of TKR. Tenholder, Clarke and Scuderi9 used a minimally-invasive medial para-patellar approach and found that their patients required less transfusion and achieved better flexion. Boerger et al10 described less blood loss, less pain, a greater range of movement and a faster return of straight leg raising, but had more complications when using a minimally-invasive subvastus TKR. Dalury and Dennis11 reported decreased pain and better movement in the early post-operative period using surgical approaches with short incisions for TKR, but noted that alignment was less accurate with these techniques. Laskin et al12 found that patients with a minimally-invasive mid-vastus approach required less analgesia in the peri-operative period, regained flexion faster and achieved functional milestones more rapidly when compared with a matched group of patients with a standard TKR. These studies suggest that minimally-invasive TKR has some peri-operative advantages over the standard procedure.
The purpose of this retrospective comparative study was to determine whether a quadriceps sparing TKR demonstrated peri-operative advantages compared with the standard approach, and to compare the short-term outcomes of the two techniques. The quadriceps sparing TKR is slightly different from the other minimally-invasive approaches. It is similar to the medial capsulotomy used for minimally-invasive unicompartmental arthroplasty and has been described previously.13,14 We hypothesised that the quadriceps sparing TKR would have similar peri-operative advantages including less pain, a decreased length of hospital stay, faster functional recovery and a greater range of movement.15,16
Patients and Methods
All the patients who had a TKR with a fixed-bearing posterior-stabilised high-flex prosthesis (Legacy High Flex, Zimmer, Warsaw, Indiana) prior to December 2002 were included in this study. There were no omissions and the patients operated on during the learning curve were also included.
They were separated into two groups. The quadriceps sparing group comprised 36 patients (41 knees) who had a TKR using a limited capsulotomy. The standard group of 34 patients (46 knees) had a primary TKR using a standard technique. All the patients were assessed before and after operation by the senior author (AJT). The assessment included a detailed history, physical examination and a radiological assessment of the knee, including standing anteroposterior, a patellar and supine lateral views.
Those having the quadriceps sparing approach weighed less than 225 1bs (102 kg), had a deformity of less than 10° in any plane, had no previous arthrotomy, a range of movement of at least 105° and a high level of motivation.
The criteria for inclusion in the standard group included knee flexion of at least 115°, a deformity of no greater than 15° in any plane, no previous arthrotomy and a well-motivated patient. A secondary indication for TKR with a high-flex prosthesis was a previous TKR on the opposite side with a poor range of movement. The patients in both groups were informed that a newly-designed prosthesis would be implanted which would, hopefully, allow for an increased range of movement of the knee after operation. The patients in the quadriceps sparing group were informed that the aims of this operative technique were to give a more rapid recovery, early walking, faster return of the range of movement of the knee and a limited period of physiotherapy.
The Institutional Review Board approval was obtained for this study.
The preferred anaesthetic technique was endotracheal intubation with general anaesthesia for the patients in both groups. However, some cases were performed using either spinal or epidural techniques at the discretion of the anaesthetist. No modifications in the anaesthetic management were made to facilitate a rapid recovery in either group. No intrathecal analgesia, pre-emptive analgesics or multimodal pain pathways were used. All the patients received parenteral and oral medication post-operatively for control of pain.
For patients in the quadriceps sparing group, the operation was performed with a leg holder because the position of the knee was constantly being changed between 20° and 70° of flexion to facilitate exposure. The incision and the medial arthrotomy extended from the superior pole of the patella to 2 cm below the tibiofemoral joint line (Fig. 1⇓). The patella was resurfaced but not everted. The distal femur was resected from the medial side with an intramedullary reference guide (Fig. 2⇓). The proximal tibia was resected using an extramedullary guide with the cut completed from the medial side. Newly-designed instruments were used to accommodate the smaller working space (Fig. 3⇓).
The standard procedure was performed using a mid-line incision and a median parapatellar arthrotomy with eversion of the patella. The bone resection was performed using milling type instruments with intramedullary referencing on the femoral side and extramedullary on the tibial.
The remaining surgical technique was similar for both groups and all the components were cemented.
Physiotherapy and use of a continuous passive movement machine was initiated on the day of surgery for the quadriceps sparing group and on the first day after operation in the standard group. A physiotherapist evaluated the patient’s pain using a visual analogue scale (VAS) at the first visit. Warfarin was used for prophylaxis against deep-vein thrombosis (DVT) in all the patients and a Doppler ultrasound was employed to look for evidence of DVT after ten days in the quadriceps sparing group and at three and ten days in the standard group. Blood loss was estimated from the amount of red cells re-infused in the recovery room with a cell saver device. Patients in the quadriceps sparing group were discharged on the second day after operation and those in the standard group on the fourth. The patients were then transferred to a rehabilitation centre for another five to seven days.
The patients were reviewed at two to three weeks following surgery, then at 6 weeks, 12 weeks, 6 months and subsequently annually. All the patients were examined and the Knee Society score determined by the senior author (AJT).
Radiographs were obtained in the post-anaesthesia care unit, on the first visit after operation, and then on an annual basis. The radiographs were measured by a blinded observer (DER) who did not participate in the surgery and had no knowledge of operative technique. All the postoperative radiographs were assessed with respect to the overall alignment of the knee and of each component. The femoral component was evaluated for varus or valgus alignment, flexion or extension, size, and anterior cortical notching. The size was determined by measuring the relationship of the posterior femoral condyle to the underlying bone on the lateral view. The tibial component was evaluated for varus or valgus alignment, slope, and size.
Student’s t-test was used for analysis of the continuous data. A two-tailed p-value of 0.05 or less was considered statistically significant. Categorical data were analysed using the likelihood ratio chi-squared test. A p-value of 0.05 or less was considered to be statistically significant. The analysis for the prevalence of radiological outliers was completed using the Fisher’s exact test with a p-value of < 0.05 for a significance. A post hoc power analysis was done to determine if the sample size was adequate to show a significant difference. A sample size of 32 knees in the quadriceps sparing group and 38 knees in the standard group provided at least 80% power to detect a difference in post-operative Knee Society scores of 6.6 points at a two-tailed alpha level of 0.05.
The demographic details of the patients and the results are summarised in Table I⇓. In the quadriceps sparing group, the mean length of follow-up was 33 months (24 to 42) and for the standard group 40 months (24 to 55). There were no infections or wound complications in either group and no revisions. There was one non-fatal pulmonary embolism, one non-fatal cardiogenic stroke, one arrhythmia, and one popliteal DVT in the quadriceps sparing group. There were five DVTs in the standard group, one mid-thigh and four below the knee. There were no peri-operative mortalities in either group. One patient in the quadriceps sparing group and one in the standard group required a manipulation under anaesthesia with a final range of movement of 80° and 105°, respectively.
A radiological outlier was defined as any knee alignment 4° or more outside of the ideal. The ideal coronal alignment was considered to be 4° of valgus, with the femoral component in 4° of valgus and the tibial implant in neutral. The ideal flexion of the femoral component was 0°. A size of component which was 4 mm too small or too large and femoral notching greater than 2 mm were also considered as outliers.
There was no statistical difference between the two groups for gender distribution, age, body mass index, pre-operative diagnosis, incidence of varus or valgus deformity and blood loss. Both groups had a similar incidence of general anaesthesia versus spinal-epidural, 89% (25 of 28) of the quadriceps sparing group and 93% (27 of 29) of the standard group had general anaesthesia. The operative time for quadriceps sparing TKR was significantly longer.
The VAS for pain was less for the quadriceps sparing group and the length of stay in hospital was shorter. The complications were similar and there was no statistically significant difference in the incidence. The quadriceps sparing group had a lower pre-operative Knee Society score (p = 0.03), but there was no statistically significant difference in post-operative Knee Society scores at final follow-up. Knee flexion after surgery was greater for the quadriceps sparing group at the first visit and remained so for the entire two years. The quadriceps sparing group maintained similar movement before and after operation (131° to 128° after two years), whereas, the standard group lost some movement (133° to 124° after two years). The final range of movement for the quadriceps sparing group at the two-year mark was statistically better than for the standard group (p < 0.05).
Radiological analysis demonstrated more outliers in the quadriceps sparing group (13 vs 5, p = 0.01) (Table II⇓). There was no statistically significant difference in any one category. When analysing coronal alignment alone, there was no statistically significant difference (5 vs 1, p = 0.10) between the two groups.
The first quadriceps sparing TKRs were completed in February 2002.13 An early report of the combined results of two surgeons (Tria and Coon) was presented at the Knee Society annual meeting.13 The paper showed that the arthroplasty was technically possible, but did not include any information about follow-up. The developers did not give the procedure a descriptive name, but during the first year it became known as the ‘quadriceps sparing’ technique. This name however, is not anatomically correct. The medial arthrotomy extends from the superior pole of the patella to 2 cm below the tibiofemoral joint line. Because the insertion of the vastus medialis may be as low as the midpoint of the patella, the arthrotomy does divide the insertion in some cases, and is therefore not always ‘quadriceps sparing’. With this proviso, the authors have continued to call the procedure ‘quadriceps sparing’ because the name and the technique have become synonymous.
The major difference between the two groups in this study was in the surgical technique. There was less postoperative pain and greater knee flexion in the patients who had the quadriceps sparing procedure. There was no difference in post-operative blood loss, or in the Knee Society scores at a minimum follow-up of two years. When using the strict criteria for radiological outliers, the accuracy of component positioning and alignment with the quadriceps sparing technique was inferior to that of a standard TKR. When specifically examining alignment in the coronal plane alone, there were more outliers with the quadriceps sparing technique, but the difference was not statistically significant.
There was a significant difference in the length of hospital stay between the two groups, primarily due to a change in the discharge protocol for patients in the quadriceps sparing group which cannot be attributed to the surgical technique alone. We started physiotherapy earlier and shortened the length of hospital stay in the quadriceps sparing group with the expectation that a less invasive procedure would allow the patients to move the knee with greater comfort. No attempt was made to expedite the recovery of the standard TKR group because the authors did not believe that the change in prosthetic design alone would enable the patients to tolerate a more aggressive approach. The changes in the post-operative management do however, invalidate the comparison for the length of hospital stay and represent a weakness of this study.
Two patients in the standard group received the high flex prosthesis because of a poor range of movement in the contralateral knee after a previous TKR with a standard prosthesis. Inclusion of these two patients did influence the mean range of movement in the standard group since if their knees were omitted the mean range of movement at the final follow-up would be 126° instead of 124°. Both values are lower than the final range of movement for the quadriceps sparing group. Although the difference in range of movement at the final follow-up was statistically significant, it does not represent a difference of clinical significance.
Quadriceps sparing TKR is a technically demanding surgical procedure compared with the standard method. The duration of the procedure was significantly longer than the standard technique and was less accurate. These findings present some concern for the designers of the operation. Since this study began, several modifications have been made. Smaller instruments have been designed and a two piece tibial component is now being used. The alignment is being confirmed intra-operatively with computer-assisted navigation. Because the instruments and tibial components are smaller, the amount of time required for the procedure has decreased dramatically. Computer-assisted navigation has also eliminated the number of radiological outliers, but further investigation of these modifications needs to be done before these claims can be verified.
Quadriceps sparing TKR was introduced to address the concerns of the patient regarding traditional TKR. In the past, TKR was a painful experience with a substantial recovery period. Post-operative pain and rehabilitation are amongst the greatest concerns for patients undergoing elective arthroplasty.17 In this study, limited invasion of the extensor mechanism decreased peri-operative pain and aided the recovery of movement.
There are a few limitations of this study which are related to its retrospective design. The two groups were not exactly the same. Another limitation was the number of patients in each group. Trends were identified which may have been statistically significant with greater numbers. The patients were carefully selected after thorough evaluation and counselling. Few patients satisfied the criteria for a TKR with the high flex prosthesis and few patients for the quadriceps sparing procedure. Of the 41 knees in the quadriceps sparing group, nine (22%) were lost to follow-up. In the standard group five patients (5 knees) died and three knees were lost to follow-up, a total of eight (17%).
The senior author is a designer of the technique and may have had bias in favour of the quadriceps sparing approach. Nevertheless, the pain scores were assessed by a physiotherapist and the radiological evaluation was performed by one of the authors (DER) who did not have knowledge of the operative procedure at the time of the measurements.
Several editorials have been written regarding the level of evidence which is appropriate for publications on new surgical procedures.18–21 When this study began, there were no published reports on quadriceps sparing TKR. This study is the first to evaluate short-term outcomes after using the technique.
It represents the experience of a single surgeon using limited criteria for inclusion and motivated patients. The quadriceps sparing approach is not appropriate for all patients or all surgeons. The technique is the least invasive form of minimally-invasive TKR and is different from other approaches. Patients had less peri-operative pain and slightly better flexion of the knee in the quadriceps sparing group compared with the standard group. At a minimum follow-up of two years, the Knee Society scores showed no statistically significant difference. The technique limits the surgeon’s visualisation of the anatomy and can lead to less accuracy, as indicated by the increase in radiological outliers. A limited approach to TKR is certainly possible and this study suggests that it produces short-term clinical results similar to a standard TKR. However, a quadriceps sparing approach takes longer to perform and it may compromise the radiological alignment.
The author or one or more of the authors have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article.
- Received April 24, 2006.
- Accepted July 6, 2006.
- © 2006 British Editorial Society of Bone and Joint Surgery