The risk of bearing dislocation in lateral unicompartmental knee arthroplasty using a mobile biconcave design

Purpose

A safety study was conducted on a cohort of 25 patients who underwent lateral unicompartmental arthroplasty with a biconcave mobile-bearing insert.

Methods

The first 25 lateral mobile-bearing unicompartmental knee replacements, performed in a general hospital by one surgeon, were prospectively reviewed, with a minimum follow-up of 1 year.

Results

One bearing dislocation occurred 4 months postsurgery. The Oxford knee score improved in all patients from a preoperative mean of 23.3 (range 8–40, SD 8.4) to a postoperative mean of 42.1 (range 23–48, SD 6.7). General patient satisfaction at a mean follow-up of 20 months was excellent in 84 %, good in 12 % and fair in 4 %. The mechanical axis as a measure on full-leg standing radiographs improved from 5.7° valgus (range 1°–16°, SD 4.1°) to 1.7° valgus (7° to ?3°, SD 2.1°). Mechanical alignment correction averaged 4.0° (range ?1° to 15°, SD 3.9°).

Conclusion

The mobile biconcave insert design in the lateral unicompartmental knee replacement seems appropriate as a innovative, anatomy imitating solution, resulting in a good clinical outcome. Still, bearing dislocation remains a concern, especially in extended indication.

Level of evidence

Case series, Level IV.     

Is bicompartmental knee arthroplasty more favourable to knee muscle strength and physical performance compared to total knee arthroplasty?

Purpose

Bicompartmental knee arthroplasty features bone and ligament sparing as unicompartmental knee arthroplasty and is presumably better in the recovery of muscle strength and function compared to total knee arthroplasty (TKA) though not previously reported in the literature. The aim of the study was to compare isokinetic knee muscle strength and physical performance in patients who underwent either bicompartmental knee arthroplasty or TKA.

Methods

Each of 24 patients (31 knees) was prospectively examined preoperatively, at 6 and 12 months after each surgery. Isokinetic knee extensor and flexor strength as well as position sense were measured using the Biodex system. Timed up and go test, stair climbing test, and the 6-min walk test were used to assess physical performance. The results of each group were also compared with those from the corresponding healthy control, respectively.

Results

Demography showed significant difference in the mean age between bicompartment (54.8 ± 5.6 years) and TKA groups (65.7 ± 6.7 years). Comparing between the two groups, knee extensor and flexor torque, hamstring/Quadriceps ratio, position sense, and physical performance were not significantly different preoperatively, at 6 and 12 months after surgery. In intra-group analysis, muscle strength and position sense at each time point were not different in both groups. In physical performance, both groups resulted in improvement in the 6-min walk test, and only TKA group showed enhancement in stair climbing test.

Conclusions

Although theoretically plausible, bicompartmental knee arthroplasty was not superior in knee muscle strength and physical performance at 1 year compared with total knee arthroplasty.

Level of evidence

II.     

An uncommon cause of cemented unicompartmental knee arthroplasty failure: fracture of metallic components

Purpose

Despite good overall clinical results, unicompartmental knee replacements (UKR) are not without their problems and failures have been reported. The most common causes of UKR failure are component loosening, poor patient selection, poor surgical technique, polyethylene wear and progression of arthritis in other compartments. The purpose of this study is to present a series of atraumatic fractures of metallic components in a UKR treated in a single orthopaedic centre.

Method

Since 1999, 121 failed unicompartmental knee arthroplasties have been referred to our centre. In six of these, atraumatic breakage of a metal component in the cemented UKR was seen and included in this study. Pre-operative alignment, BMI and implant longevity were documented. The femoral implant failed in 4 patients and the tibial implant in a further 2.

Results

All the femoral implant fractures occurred within 3 years of UKR surgery (mean: 22.2 months, SD: 10.6 months). Tibial implant breakage occurred at a mean of 8.5 years (SD: 2.4 months) following UKR. All patients were treated with conversion to a navigated total knee replacement. A primary total knee arthroplasty was used in all cases with one patient requiring a tibial component incorporating a wedge and stem following breakage of the original UKR tibial implant.

Conclusion

Fracture of the metallic components is a potential cause of failure of unicompartmental knee arthroplasty. In our experience, the incidence of this complication was 4.9 % of all UKR failures. Patients with a BMI greater than 30 and a progressive deterioration in limb alignment were at greater risk.

Level of evidence

IV.     

Early migration of the cemented tibial component of unicompartmental knee arthroplasty: a radiostereometry study

Purpose

Unicompartmental knee arthroplasty has good clinical results but high revision rates. A unicompartmental knee arthroplasty design features an all-polyethylene and conforming tibial component, and we hypothesized that this may put at risk its fixation. Implant-to-bone micromotion was measured together with relevant clinical outcomes.

Methods

The migration of the tibial component in twenty patients was measured at 3, 6, 12 and 24 months, using standard radiostereometry, along with the relevant clinical outcomes using the IKS scoring system.

Results

The eighteen arthroplasties at 24 months were found successful, with very good functional (mean 87.7; SD 15.4) and knee scores (mean 94.8; SD 10.1). The means and the standard deviations of the maximum total point motion (MTPM) for the four follow-ups were, respectively, as small as 0.4 ± 0.1 mm, 0.6 ± 0.2 mm, 0.6 ± 0.3 mm and 0.7 ± 0.3 mm, an average over all patients but one. In this knee, these were 1.6, 2.1, 2.4 and 2.2 mm, therefore not at high risk of aseptic loosening according to the literature. Only one knee was found at this risk, having the MTPM from 12 to 24 months of 0.5 mm, and the component moving and sinking medially, and rising laterally.

Conclusion

At 2-year follow-up, a successful implant-to-bone fixation can be achieved in conforming all-polyethylene cemented tibial component together with excellent clinical outcomes.

Level of evidence

Prognostic studies, Level I.     

Satisfactory outcomes following combined unicompartmental knee replacement and anterior cruciate ligament reconstruction

Purpose

There exist limited options for treatment of patients with combined medial compartment arthritis and anterior cruciate ligament (ACL) deficiency. Ideal treatment is one that offers lasting relief of symptoms not compromising any future surgery. Unicompartmental knee replacement has shown consistently good results in the relatively young and active population, but there is a high reported incidence of failure up to 20%, if performed in ACL-deficient knees. One of the recognized treatment modality is combined ACL reconstruction and unicompartmental arthroplasty. A systematic review was conducted looking at the demographics, techniques, complications and outcome of combined ACL reconstruction with unicompartmental knee arthroplasty.

Methods

A systematic literature search within the online Medline, PubMed Database, EMBASE, Web of Science, Cochrane and Google Scholar was carried out until October 2016 to identify relevant articles. A study was defined eligible if it met the following inclusion criteria: the surgical procedure combined unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction; patient’s clinical and/or functional outcomes were reported; any complications intra-operatively and post-operatively were reported; and the full-text articles, written in English, German, Italian, Dutch or Spanish, were available. Quality and risk of bias assessments were done using standardized criteria set.

Results

A total of 8 studies met the inclusion criteria encompassing 186 patients who were treated with simultaneous ACL reconstruction and unicompartmental knee arthroplasty. The mean age was 50.5 years (range from 44 to 56) with a mean follow-up of 37.6 months (range from 24 to 60). There was an improvement in mean Oxford Score from 27.5 to 36.8. Complications reported included tibial inlay dislocation (n = 3), conversion to a total knee arthroplasty (n = 1), infection requiring two-stage revision (n = 2), deep-vein thrombosis (n = 1), stiffness requiring manipulation under anaesthesia (n = 1), retropatellar pain requiring arthroscopic adhesiolysis (n = 1).

Conclusion

Unicompartmental knee arthroplasty combined with ACL reconstruction can be a valid treatment option for selected patients, with combined medial unicompartmental knee osteoarthritis and ACL deficiency.

Level of evidence

Systematic Review of Level IV Studies, Level IV.

     

Knee arthroplasty and bleeding: when to remove drainages

Purpose

The aim of this study is an attempt to clarify the productive time of drainages as we find that the use of drains in knee arthroplasty is controversial, and there is no consensus regarding their length–time maintenance. We analysed the survival curve of bleeding within three surgical techniques for knee arthroplasty and the effect of two variables on survival curve.

Methods

One hundred and eighty-eight out of 234 knees were included in the study, and patients were divided into three groups according to the surgical technique: conventional total knee arthroplasty (TKA), subvastus TKA and unicompartmental knee arthroplasty. Variables of study were type of surgery, number and placement of drains.

Results

Mean of survival curve for postoperative bleeding time was 16 h (95 % CI: 15.4; 16.6). The risk for longer bleeding increased 1.38-fold with each additional drain used (95 % CI 1.1; 1.8).

Conclusions

According to the present study, drains can be safely removed at around 17 h postoperative. Bleeding time reduces as less drains are applied.

Level of evidence

Therapeutic study, Level III     

Dutch translation of the Kujala Anterior Knee Pain Scale and validation in patients after knee arthroplasty

Purpose

To translate and validate the Kujala Anterior Knee Pain Scale (AKPS) in patients who have undergone total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) and evaluate the internal consistency, construct validity and ceiling or floor effect.

Methods

After standard forward and backward translation was performed, 302 patients who have received a TKA or UKA filled out the AKPS together with Hospital for Special Surgery (HSS) patella score, visual analogue score (VAS) for pain, the Oxford 12-item questionnaire and the SF-36 at follow-up. The internal consistency was tested using Cronbach’s α coefficient. The construct validity was assessed using Spearman’s rank correlation (R) to test for correlations between the AKPS and VAS HSS, HSS patella score, VAS month, Oxford 12-item questionnaire and SF-36 subscales. Ceiling or floor effects are given in percentage of patients giving a maximum or minimum score.

Results

The internal reliability of the AKPS is acceptable with a Cronbach’s α of 0.81 in patients after TKA or UKA. A high correlation was found between the AKPS and the Oxford 12-item questionnaire (R = 0.81). Moderate correlations were found with the VAS month (R = 0.63), HSS patella score (R = 0.51) and SF-36 subscales physical functioning (R = 0.59), role-physical (R = 0.59), bodily pain (R = 0.57). Other correlations were poor, therefore indicating a good convergent and divergent validity. Ceiling effects were observed for the HSS patella score (31 %), VAS HSS (51 %), VAS pain (19 %), SF36-RP (46 %), SF36-RE (80 %) and SF36-BP (24 %). No ceiling or floor effect was found for the AKPS, Oxford 12-item and the other SF36 domains.

Conclusions

The AKPS appears to be reliable and valid in patients after knee arthroplasty, with no ceiling and floor effects, and can be used to assess anterior knee pain in patient who underwent joint replacement surgery.

Level of evidence

Diagnostic study, Level I.     

Tibial component alignment and risk of loosening in unicompartmental knee arthroplasty: a radiographic and radiostereometric study

Purpose

Unicompartmental knee arthroplasty (UKA) has shown a higher rate of revision compared with total knee arthroplasty. The success of UKA depends on prosthesis component alignment, fixation and soft tissue integrity. The tibial cut is the crucial surgical step. The hypothesis of the present study is that tibial component malalignment is correlated with its risk of loosening in UKA.

Methods

This study was performed in twenty-three patients undergoing primary cemented unicompartmental knee arthroplasties. Translations and rotations of the tibial component and the maximum total point motion (MTPM) were measured using radiostereometric analysis at 3, 6, 12 and 24 months. Standard radiological evaluations were also performed immediately before and after surgery. Varus/valgus and posterior slope of the tibial component and tibial–femoral axes were correlated with radiostereometric micro-motion. A survival analysis was also performed at an average of 5.9 years by contacting patients by phone.

Results

Varus alignment of the tibial component was significantly correlated with MTPM, anterior tibial sinking, varus rotation and anterior and medial translations from radiostereometry. The posterior slope of the tibial component was correlated with external rotation. The survival rate at an average of 5.9 years was 89 %. The two patients who underwent revision presented a tibial component varus angle of 10° for both.

Conclusions

There is correlation between varus orientation of the tibial component and MTPM from radiostereometry in unicompartmental knee arthroplasties. Particularly, a misalignment in varus larger than 5° could lead to risk of loosening the tibial component.

Level of evidence

Prognostic studies—retrospective study, Level II.     

Extended sagittal saw cut significantly reduces fracture load in cementless unicompartmental knee arthroplasty compared to cemented tibia plateaus: an experimental cadaver study

Purpose

Periprosthetic tibial plateau fractures represent a rare but serious complication in unicompartmental knee arthroplasty and are associated with extended sagittal tibial bone cuts. These can occur during the surgery, weaken the posterior cortex of the tibia and are associated with periprosthetic tibial plateau fractures. Although excellent long-term results have been reported with cemented unicompartmental knee arthroplasty, there is high interest in cementless fixation. The aim of the study was to compare fracture loads of cementless and cemented unicompartmental knee arthroplasty.

Methods

Tibial components of the Oxford Uni were implanted in six paired fresh-frozen tibiae with a defined extended saw cut (10°) at the dorsal cortex of each specimen. In one set, surgery was performed with cement fixation, and in the other, cementless components were implanted. Vertical loads were then applied under standardised conditions to fracture the specimens.

Results

Median loads of 3.7 (0.7–6.9)?kN led to fractures in the cemented group, whereas cementless fixated tibiae fractured with a median load of 1.6 (0.2–4.3)?kN (P?=?0.02).

Conclusion

The loading capacity in tibiae with cementless components is significantly less compared to cemented fixation. The results show that in case of an extended sagittal bone cut patients especially those with poor bone quality who are treated with a cementless unicompartmental knee arthroplasty are at higher risk for periprosthetic tibial fractures.     

Preoperative asymmetry in load distribution during quite stance persist following total knee arthroplasty

Purpose

Preoperative function has been shown to persist posttotal knee arthroplasty. However, it remains unclear whether asymmetries are task specific. Therefore, we investigated postoperative asymmetries in loading during quiet stance and walking gait.

Methods

Ten patients with end-stage knee osteoarthritis scheduled for total knee arthroplasty were studied at baseline (preoperative), 6-week, 3- and 6-month postoperative. Load distribution and balance were quantified during quiet stance. Furthermore, dynamic loading was quantified during walking gait. Patient satisfaction was assessed using the Knee Osteoarthritis and injury Outcome Score.

Results

Preoperatively, load distribution was significantly different between limbs, with approximately 70 % of the load through the contralateral or ‘good’ side. Asymmetries persisted and up to 6-month postoperative during quiet stance. No significant change was found in balance. During walking, preoperative loading asymmetry was present; however, no significant postoperative loading asymmetries were identified.

Conclusions

Total knee arthroplasty does not appear to significantly change load distribution or balance 6-month postoperative during quiet stance; however, during walking gait, symmetry appears to be restored. This could be potentially improved through enhanced rehabilitation.

Level of evidence

Therapeutic study, Level IV.     

Less anterior knee pain with a routine lateral release in total knee arthroplasty without patellar resurfacing: a prospective,randomized study

Purpose

Anterior knee pain is a major cause of complaint in total knee arthroplasty (TKA) without patellar resurfacing. The concept of improved patellar tracking and decreased retropatellar contact pressure for lateral retinacular release theoretically suggests that patients with lateral retinacular release in TKA would achieve a lower incidence of anterior knee pain when compared without lateral retinacular release. We sought to determine (1) whether those patients who received a routine lateral retinacular release in TKA would attain lower incidence of anterior knee pain as compared to patients who received TKA without lateral retinacular release and (2) whether lateral retinacular release would increase the lateral retinacular release-related complications.

Methods

A total of 148 patients who underwent TKA with the use of the Gemini MK II mobile bearing were randomized to receive either routine lateral retinacular release (intervention group) or not (control group). Patients were assessed by the visual analogue scale for anterior knee pain, the Knee Society clinical scoring system of knee score and function score, and patellar score for clinical function. Patients’ satisfaction and lateral retinacular release-related complications were also evaluated.

Results

The overall incidence of anterior knee pain in the intervention group at 18 months follow-up was 5.6 %, while that of the control group was 20.6 % (p = 0.009). No statistical difference was detected between the two groups in terms of lateral retinacular release-related complications (n.s.), patients’ satisfaction (n.s.), knee score (n.s.), function score (n.s.), and patellar score (n.s.) at 18 months follow-up.

Conclusion

The present study suggests that routine lateral retinacular release can reduce anterior knee pain and does not increase lateral retinacular release-related complications, in TKA with the use of the Gemini MK II mobile bearing without patellar resurfacing.

Level of evidence

Therapeutic, Level I.     

Kinematics of the knee after unicompartmental arthroplasty is not the same as normal and is similar to the kinematics of the knee with osteoarthritis

Purpose

It is common to assert that restoration of normal knee kinematics is essential for the best functional result after knee arthroplasty. Previous studies using the progression of the geometric centre axis have suggested that kinematics after unicompartmental arthroplasty is markedly different from the normal. For this study, the transepicondylar axis was used because this axis is closer to the flexion axis and should be a better reference for motion. The following hypothesis was tested: the transepicondylar axis would again show that the postoperative kinematics does not restore normal motion and is closer to that before replacement.

Methods

Seventeen osteoarthritic knees were tested before and after unicompartmental arthroplasty using a three-dimensional to two-dimensional registration technique tracking the transepicondylar axis to calculate translation and rotation of this axis. Results were compared for the seventeen knees before and after arthroplasty and were compared to the normal knee as measured in our previous study.

Results

Similar motion patterns in the pre- and postoperative knees were shown but both the pre- and postoperative motion were markedly different from the normal knee.

Conclusions

This result supported our hypothesis. The clinical relevance is that medial unicompartmental arthroplasty cannot restore the motion of the knee to normal in the living knee. Therefore, it would be expected that the patient for unicompartmental knee might not feel normal. It may not be possible depending on ligaments alone to restore the knee to normal, and the changes in the articular shapes and the surgical procedure may also be necessary.

Level of evidence

IV.     

Medial femoral head border is a reliable and reproducible reference for axis determination for femoral component of unicompartmental knee arthroplasty

Purpose

The femoral component should be implanted parallel to the mechanical axis in unicompartmental knee arthroplasty. It was hypothesised that a line between medial femoral condyle centres and medial border of femoral head will be parallel to the mechanical axis; this study set out to examine this hypothesis.

Methods

One hundred X-rays in fifty patients were included for this study. Long-leg standing X-rays including hip and ankle with patellae facing forwards were obtained. On these films, we measured the angle, α, between mechanical axis and the line between the femoral head centre and knee centre (medial mechanical axis), and the angle, β, between the medial mechanical axis and a line between medial femoral condyle and femoral head centre.

Results

The average value of α was 0.1 ± 0.5° and the average value of β 3.0° ± 0.3°. These data indicate that mechanical axis and medial mechanical axis are virtually parallel to each other.

Conclusion

As medial femoral head border is easily identified fluoroscopically, it is a reliable landmark for orientating the femoral component of medial UKA.

Level of evidence

Case series with no comparison group, Level IV.     

Proprioception after bicruciate-retaining total knee arthroplasty is comparable to unicompartmental knee arthroplasty

Purpose

Rising expectations in functional performance of total knee joints are inciting further improvement of knee arthroplasty implants. From a patient-centred view, bicruciate-retaining models provide a more natural feeling knee. However, there is no evidence of functional advantage for these implants. The aim of this study was to evaluate balance ability as a measure of proprioception in patients with a bicruciate-retaining total knee arthroplasty.

Methods

A prospective, controlled trial was conducted to compare balance ability in 60 patients after arthroplasty of the knee for osteoarthritis. We compared patients with a bicruciate-retaining knee arthroplasty (BCR group) to a control group of patients with a medial unicompartmental knee arthroplasty (UKA group) and another control group of patients with a posterior stabilized total knee arthroplasty (PS group). The patient population comprised 30 women (50.0 %) and 30 men in three cohorts of 20 each. The mean age was 62.1 ± 8.0 years (range 43–78). Patients were evaluated preoperatively and 9 months post-operatively. The evaluation included clinical, radiological, and balance testing—a single-leg stance with eyes closed compared to eyes open. The difference in area of sway between eyes closed and eyes open represents static balance ability after knee arthroplasty.

Results

Perioperative data showed that there was no intra-operative fracture of the intercondylar eminence. There was a decreased post-operative knee extension 9 months post-operative in the BCR group, which was not clinically relevant in any case. We recorded a lower difference in the area of sway between eyes closed and eyes open (ΔA _(ec–eo)) for the BCR group (p = 0.01) and the UKA group (p = 0.04) compared to the PS group.

Conclusions

This study found superior static balance ability after preservation of both cruciate ligaments in arthroplasty of the knee, indicating superior proprioceptive function. Hence, BCR implants could provide improved functional properties. Superior proprioceptive function of bicruciate-retaining implants can be an important factor in implant selection. Further prospective, randomized studies to investigate kinematics and long-term survivorship of bicruciate-retaining implants are needed.

Level of evidence

II.

     

Preoperative pain location is a poor predictor of outcome after Oxford unicompartmental knee arthroplasty at 1 and 5 years

Purpose

Indications for unicompartmental knee arthroplasty (UKA) vary between units. Some authors have suggested, and many surgeons believe, that medial UKA should only be performed in patients who localise their pain to the medial joint line. This is despite research showing a poor correlation between patient-reported location of pain and radiological or operative findings in osteoarthritis. The aim of this study is to determine the effect of patient-reported preoperative pain location and functional outcome of UKA at 1 and 5 years.

Methods

Preoperative pain location data were collected for 406 knees (380 patients) undergoing Oxford medial UKA. Oxford Knee Score, American Knee Society Scores and Tegner activity scale were recorded preoperatively and at follow-up; 272/406 (67 %) had pure medial pain, 25/406 (6 %) had pure anterior knee pain, and 109/406 (27 %) had mixed or generalised pain. None had pure lateral pain. The primary outcome interval is 1 year; 132/406 patients had attained 5 years by the time of analysis, and their 5-year data are presented.

Results

At 1 and 5 years, each group had improved significantly by each measure [mean ΔOKS 15.6 (SD 8.9) at year 1, 16.3 (9.3) at year 5]. There was no difference between the groups, nor between patients with and without anterior knee pain or isolated medial pain.

Conclusions

No correlation is demonstrated between preoperative pain location and outcome. We conclude that localised medial pain should not be a prerequisite to UKA and that it may be performed in patients with generalised or anterior knee pain.

Level of evidence

Therapeutic, Level II.     

C-reactive protein (CRP) in different types of minimally invasive knee arthroplasty

Purpose

C-reactive protein (CRP) is an acute-phase biomarker responding to surgical trauma. Typically, a first peak is observed at day 2 with a reduction at day 4 and normalization 3–6 weeks after surgery. CRP is often linked to prosthetic joint infection when elevated values are present longer time after surgery. The aim of this study was to analyse the kinetics of CRP in different types of minimally invasive (MI) arthroplasty and to observe if there were significant differences in between MI total knee arthroplasty (TKA), patient-specific instruments (PSI) TKA and unicompartmental arthroplasty (UKA).

Materials and methods

Three hundred and seventy-two patients were prospectively studied with a blood test measuring CRP at day 2, 4, 21 and 42 in 3 different groups of patients: 257 MI TKA, 55 PSI TKA and 60 UKA. Mean peak values and kinetics were compared in between different groups of MI arthroplasty.

Results

There was a significant age difference in the three MI arthroplasty groups. The difference in mean age for the conventional MI TKA group of 68.8 ± 9.8 years, 58.5 ± 11.7 years for the unicompartmental group (P < 0.05) and 63.3 ± 9.6 years for the PSI group (P < 0.05) was significant. Mean CRP level, for the entire study group, on day 2 was 16.7 ± 8.8 mg/dl that gradually decreased to 13.6 ± 7.8 mg/dl on day 4. On day 21 and 42, median CRP level was 0.6 (0–20) and 0.4 (0–7) mg/dl, respectively. Peak CRP values were lower for UKA compared to TKA at day 2 (11.6 vs. 17.5 mg/dl) and day 4 (8.0 vs. 15 mg/dl), but this was not observed for PSI–assisted arthroplasty (18.9 vs. 17.5 mg/dl). There was a trend for faster CRP normalization in UKA compared to the two other groups at day 21 and at day 42 and for PSI TKA to have a lower mean level at 4 days (12.9 vs. 15 mg/dl). There was no statistical difference in the normalization rate of PSI–assisted versus MI TKA.

Conclusion

Kinetics of CRP in MI arthroplasty are identical to the published kinetics of conventional TKA. Most patients normalize CRP at 3 weeks; however, 18 % does not by 6 weeks. This is not a sign of early prosthetic joint infection. Peak values are significantly lower for UKA but not for PSI TKA.

Level of evidence

II.     

Reconstruction of the extensor mechanism with fresh-frozen tendon allograft in total knee arthroplasty

Purpose

Patellar tendon rupture after total knee replacement is a rare and highly limiting injury with multifactorial aetiology. Many reconstruction techniques have been described with not very predictable results. The use of allografts has been accepted as a suitable solution.

Methods

A series of seven patients with patellar tendon rupture treated with fresh-frozen tendon allograft reconstruction after knee arthroplasty is presented.

Results

Median follow-up is 25 months (20–31). Functional assessment improved, and the knee society score and knee functional score improved from 26 and 16 to 82 and 55, respectively. Median extension lag was 5° (0°–20°), with a median range of motion of 95° (70–100). Radiological study showed a rise of the patella of 22.26 mm.

Conclusion

The use of fresh-frozen allografts as a solution to patellar tendon ruptures after knee arthroplasty seems to provide acceptable results. Increased patellar height does not seem to affect functionality.

Level of evidence

Case series, Level IV.     

Joint line reconstruction in medial unicompartmental knee arthroplasty: development and validation of a measurement method

Purpose

Preservation of the joint line in total knee arthroplasty (TKA) has shown to be an important factor for the long-term outcome, especially in revision TKA. For unicompartmental knee arthroplasty (UKA), the role of the joint line has neither been investigated nor is it consciously respected during implantation. Thus, the aim was to establish and validate a standardised measurement method to determine the joint line in UKA.

Methods

As there is no established method to evaluate changes in the joint line radiologically, we introduced two methods and correlated them. The methods were first validated in a cadaver model by a controlled rotational study. Then, the joint line of 29 patients with an UKA (Oxford, Biomet, Bridgend, UK) was determined on pre- and post-operative radiographs. Both methods were tested by intra- and inter-rater reliability.

Results

Both methods showed a good intra- and inter-rater reliability. Furthermore, there was only little bias in agreement between both methods and raters. Measurements of the 29 UKA patients revealed that the joint line was more distally by a mean of 4.4 ± 1.2 mm after surgery.

Conclusions

The study provides for the first time a reliable and standardised measurement tool to determine the changes in the joint line after implantation of an UKA. The instrument should be used in further studies to evaluate the impact of the joint line on the long-term outcome, the load in the two non-replaced knee compartments and on the ligaments.

Level of evidence

Diagnostic study without a universally applied ‘gold’ standard, Level III.     

Toe-out angle changes after total knee arthroplasty in patients with varus knee osteoarthritis

Purpose

Toeing-out is a commonly proposed kinematic variable that has been suggested to reduce external knee adduction moment. Analyses of the toe-out angle after total knee arthroplasty (TKA) are useful for obtaining a proper understanding of the abnormal gait caused by varus knee osteoarthritis (OA), as well as performing rehabilitation after arthroplasty. Changes in the toe-out angle after arthroplasty have not yet been defined or analysed.

Methods

The study population consisted of 32 knees in 32 patients with varus knee OA who underwent TKA. The femorotibial angle was evaluated on standing anteroposterior radiographs before and after arthroplasty. The subjects underwent three-dimensional motion capture analyses to measure gait parameters (walking speed, cadence, stride length, step length, step width and the relative length of the single-limb support (SLS) percentage of one gait cycle) and the maximal hip adduction angle in the stance phase, the trunk lean angle in the coronal plane and the toe-out angle before and 4 weeks after arthroplasty.

Results

The femorotibial angle on the side of arthroplasty improved after surgery. Among the measured gait parameters, only the SLS percentage increased significantly. The hip adduction angle and toe-out angle on the side of arthroplasty increased significantly after surgery.

Conclusions

The knee alignment and hip adduction angle in the coronal plane and SLS phase were normalized after arthroplasty. The increase in the toe-out angle after arthroplasty may be attributable to the restoration of a normal knee alignment. These findings contribute to obtaining a proper understanding of the abnormal gait caused by varus knee OA and are useful for orthopaedic surgeons and rehabilitation therapists when treating patients after arthroplasty.

Level of evidence

Prospective study, Level II.