Tibial Osteotomy

The Tibial Osteotomy recommendation has been downgraded one level because of inconsistent evidence.

High tibial osteotomy (HTO) has been used for pain relief of medial compartment knee osteoarthritis. Realigning the varus knee provides mechanical decompression of the medial compartment. An osteotomy line is created in the proximal tibial and either a wedge defect is created by opening the medial cortex and held open with a wedge or plate and screw hardware, or a lateral wedge is removed and secured commonly with staples or wires. In the Nerhus 2017 study, patients continued to show improvement 6 and 12 months post-operatively. Historical studies have reported pain reduction with survival rates approximately 70% at 10 years (“survival” usually interpreted with endpoint conversion to replacement) (van Outeren cites Brouwer 2014 and Niinimaki 2012).

Many studies available for review by the workgroup compared various techniques of osteotomy in randomized studies. Ogawa 2019 found osteotomy distal to the tibial tubercle to be superior to proximal osteotomy for opening wedge procedure with regard to patellofemoral pain. Arthroscopic evaluation of the knee joint at time of osteotomy and second look at time of hardware removal showed less patellar and trochlear degeneration with the distal osteotomy group.

Nerhus 2017 saw no significant functional difference between surgical patients randomized to either opening or closing wedge, with all showing improvement.

Duivenvoorden 2014 reported improved HSS scores from 71 to 81 at 6 years post-op. VAS scores improved from 6.1 baseline to a statistically significant difference at follow up of 4.0 in the opening wedge patients and 3.2 with the closing wedge (albeit no statistical difference between the groups). It should be noted that patients lost to follow up started with a VAS score 6.6, thus tempering analysis of late results.

Brouwer 2006 performed a prospective randomized trial comparing closing wedge and opening wedge techniques. Closing wedge was secured with two surgical staples and opening wedge with a Puddu plate. After one-year VAS score had improved from 6.1 to 3.6.

Van Outeren 2017 is perhaps the closest attempt to a large randomized control trial between surgery and non-operative management. However, this is still not a highest quality randomized control trial. The researchers gathered two different groups of patients at two different hospitals. The first group underwent randomization to valgus bracing versus usual care. The second group was randomized to HTO with either opening wedge or closing wedge osteotomy.  The groups were matched for baseline characteristics. They found HTO more effective in pain reduction compared to non-operative methods. VAS changed from baseline 6.2 in the surgery group to 3.8 post-op. Control group improved from 6.4 to 5.0. Function was improved only in comparison of surgical patients to usual care treatment. 

The Wu 2017 study evaluated people with bilateral OA with pain around medial part of the knee. The more degenerative knee got proximal tibial osteotomy, and the other knee got usual non-operative care. The study authors included a table of individual patient data, which allowed a model that controlled for differences in baseline knee society function scores between the knees to be run. With this model, the odds ratio of achieving satisfactory knee society function scores (defined as score >= 80) with osteotomy vs. non-operative treatment was 7.51(CI 1.094, 51.6).

Benefits/Harms of Implementation

As with any osteotomy surgery, bone healing and hardware complications can occur. Incomplete osteotomy can lead to unexpected fracture at the point of correction (Getgood 2011). Neurologic injury is feared but uncommon. 2 of 35 patients in both closing wedge and opening wedge groups under Nerhus et al. 2017. Duivenvoorden had only one patient with peroneal nerve injury (closing wedge group) and Brouwer only 1 of 92 (also closing wedge group). Hardware removal appeared more common with medial opening wedge techniques. Limb length discrepancy is also increased with the opening wedge technique (Kim et al. 2016). Van Outeren had non-union of the osteotomy site only in 2 opening wedge patients. Duivenvoorden found opening wedge HTO to have more complications. However, non-union of the osteotomy was more common with their closing wedge technique (Duivenvoorden 2014). Brouwer on their other hand concluded their close wedge technique to have achieved more accurate correction with less morbidity.

The increase valgus angle across the knee will change patellar tracking, as noted above by Ogawa et al. 2019. In Song et al. 2012 no patient at baseline reported anterior knee pain. Although no significant difference was seen between their closing wedge and opening wedge groups, 30% of their patients had various levels of anterior knee pain, including 9% with moderate and 6% with severe anterior knee pain (minimum follow up 3 years).

Nerhus 2017 at two years follow up reported only 1 (closing wedge group) of their total 70 patients as revision to arthroplasty. Duivenvoorden 2014 had six year follow up and reported conversion to TKA in 10 of 45 closing wedge HTO patients and 3 of 45 in the opening wedge group.

Outcome Importance

Despite the lack of a true RCT comparing HTO to non-operative management, the studies reviewed by the workgroup all agree with the premise that pain is reduced by HTO. There appear to be relatively equal outcomes whether HTO is achieved with lateral or opening wedge surgical technique. Opening wedge osteotomy distal to the tibial tubercle appears to be preferred, according to the single study examining this aspect of surgical technique (Ogawa 2019).

Cost Effectiveness/Resource Utilization

Hardware removal was relatively common, and the second surgery will add expense to the total endeavor. For reference, Brouwer reported hardware removal in 11 of 47 closing wedge cases and 27 of 45 with opening wedge HTO. Nerhus reported metal removal in 4 of 35 closing wedge cases and 8 of 35 in the opening wedge group.

Conversion to knee arthroplasty is the most expensive late effect of the procedure. As years increase post-op, conversion rates to TKA increase. No studies were identified which adequately addressed the cost-benefit of knee replacement options versus osteotomy.

Acceptability

In select patients with isolated medial compartment arthritis, there appear to be adequate short-term results with regard to pain and function in those patients undergoing surgery.

The quality of HTO results will be dependent upon the skill and experience of the operating surgeon and the cooperation of a patient to understand he or she is entering into a post-op state with altered anatomy and a prognosis imperfectly known in comparison to other options.

Feasibility

Van Outeren rightly questions the benefits of surgical treatment versus brace treatment. Their study had only one-year follow-up and 25 of 60 patients initially in the brace group dropped. They were not optimistic for long term utility and/or compliance of brace treatment.

Future Research

Previous studies have addressed outcomes when converting UKA to TKA and likewise for converting HTO to TKA. Studies looking at functional improvement and pain relief of HTO in direct comparison to knee replacement surgery (total or partial) would be of great value to our collective knowledge base, especially if such a study could track patients from baseline into HTO versus UKA and then long term to TKA. It is unlikely such a study could be performed prospectively over such a long time, yet data from a registry might prove fruitful.