My personal experience with short stems have a maximum of 4 years follow, the experience is satisfactory but the follow-up is short and I can not make comparisons with conventional cementless models in which I have experience of over 20 years. I think that is an option for the treatment of osteoarthritis in young active individuals

Antonio,

What style short stem do you use? Do you have any contraindications? Have you altered your post-operative routine? Finally what is your surgical approach and did you have any concerns or problems in switching to short stems?

Regards,

Tim

I have no experience with short stems. I find the idea to be good, especially for preserving bone stock that is very important in case of later revision for loosening. Anyway, the indications seem to be very narrow (young patients).

Furthermore, my 30 years of experience with conventional stems is very satisfactory and coincides entirely with the long-term results published by the Swedish Hip Registry. The long-term outcome reports on Charnley and Mueller prostheses are also very convincing. I believe the "low friction principle" has stood the test of time, and in my opinion is the greatest contribution in the field of THA at all.

This opinon of mine does not mean that no innovations should be tried and introduced in the medical practice. This is the everlasting strive for perfectioning. Anyway, I am looking forward to long-term outcome studies on the short stems that are lacking sofar. The other thing that impresses me and makes me very attentive is the avalanche of short stem prostheses that overwhelm the market. There are also different concepts (curved short stem, lateral flare stem, etc.). How can we choose the best model ?

Panayot,

I could not agree with you more. Professor Charles O. Bechtol was my mentor who of course was a strong advocate of Sir John. My observations over the years as a hip designed is that the best changes are incremental. The S-Rom which I was lucky enough to be part of that developmental team was just that. That stem evolved out of the Sivash which was far from being a success. But it did make some contributions. First cementless stem made of titanium with a cobalt chrome reassembled head. The design concept of femoral tapered sleeves, and distal flutes which came from the Swanson IM fluted rod.

Mueller was the first to add different neck lengths and also added a high femoral offset. His teaching of preoperative templating was a significant advancement at the time. Bechtol copied Charley style stem, took from Mueller the different offerings of neck lengths and improved the instruments and the Bechtol hip was introduced in the 1970s.

In my own development the S-Rom has been very successful both clinically and in the market place. However, the interest in being more conservative which I created Pipino I looked at was there a gap in the current product offerings and if so how best to address.I reviewed  Pipino's 30 years of working on his short curved neck retaining stem and was impressed with his concept and dedication towards his project. In taking his CME courses I found some findings to be lacking. He was still encountering some medial calcar bone loss. His stem offering of to curvatures seemed at times confusing plus added to inventory of implants and instruments. On the other hand his results were as good as any of the conventional cementless stems.

So in reflection the main factor to the success of the S-Rom was the stem geometry provided for initial short term stability while also providing the potential for long-term fixation. The down size of the S-Rom was it required a good understanding of the design and required surgical technique to make it reproducible. The straight stem required considerable effort to stay lateral for preparation and insertion of the stem. Also if you needed to remove the stem it could be very challenging.

So that laid out some design goals for me in developing the TSI™ Tissue Sparing Implant concept. I was confined by Pipino, Freeman, Townley and Whitside that there was significant value in preserving the femoral neck. The potential advantages of a short stems was attractive. I believe that Mueller and Thompson were correct with the concept of a curved stem (although their individual designs were lacking). The S-Rom clearly demonstrated the requirement of initial implant to bone stability. Pipino's two medial curve stem offerings was confusing.

So out of this intense review process the design features of the TSI were developed:

1. a short curved neck preserving stem (reduced bending and torsional moments)

2. A neutral medial curve for simplicity

Went back to rasping not broaching the medial curve. Need to shape the host bone to the medial curve of the patient.

3. Stem is a curved trapezoidal style stem for enhanced torsional stability.

4. A lateral t-back feature for enhance torsional resistance

5. A proximal conical flare to increase compressive loads to the medial calcar.

6. Proximal only porous coating for fixation and a distal polished stem for reduced distal fixation.

7, A sagittal distal slot to reduce distal load transfer

8. Retrievable features for minor bone loss in case of revision

9 One tray of simple cost effective instruments.

This of course is just an overview but each design feature has been proven in the past in one or more stem offerings but never in this combination. Then of course proper FEA modeling and mechanical testing to validate the concept.

Now comes the scary part of beginning clinical trials. A tightly control surgical/clinical team of Master Hip Surgeons and of course full documentation and timely publications of all results.

Our TSI™ Study Group findings from 2007 have been that there is a learning curve for achieving stability in the neck versus metaphyseal/diaphyseal fixation. Short learning curve but very definitive. Potential increased mechanical impingement so careful examination and removal of osteophytes are necessary. Do not go below a 32 mm head diameter. If you ca not get to 32 mm use a mobile bearing design. Intraoperative x-rays are very helpful to ensure proper stem size. Do not overstuff distal fit in type Door A bone. The distal stem is gust a guide. Slight varus or valgus does not seem to have a clinical negative finding. Slight varus does demonstrated increased medial calcar density versus valgus. Proper conical flare does promote increased medical calcar bone density. Retained femoral neck in the posterior approach does provide for easier repair of the capsule. Medial curvature does make the direct anterior approach easier for femoral canal preparation and stem insertion.

We have seen implantation in all Door bone types (A,B &C). We have had some very good results in type C bone but are very cautious in this area. Retrievability and conversion with minor bone loss is possible.

With all that said can I say this is a better concept then that of Joe Fetto's lateral flare design. No, Joe is a friend of mine and I know his results and have confidence his work and results. However do I think his stem is slightly more challenging to implant. Yes, because of the need to go lateral. I also believe removal is more difficult. That is why we (JISRF) created a stem classification system for better understanding and comparison of design concepts.

I have written two books chapters (in print) on the subject of short stems and there is a lack of long-term follow but I am optimistic in what I am seeing across the board with short stems.

I do worry about the trend at least in the States of early full weight bearing and increased physical activity. I am still of the belief  that the bone fracture healing response is 6-8 weeks and we should guard our reconstructive hips for that period of time.

This is a high area of interest for me and I invite any interested part to contact me : www.jisrf.org / [email protected]

Regards,

Tim

Thank you, Tim, for your comprehensive posting. It is really very interesting. I would be also interested in reading your books chapters (in print). Anyway, I would  be interested in reading reports on long-term results from short stem prostheses.  

Regards,

Panayot

Panayot,

I would be happy to send you the galley proofs publication dates are later this year. Currently writing" Evolution and Use of Short and Neck Sparing Stems in DAA Surgery" that will be published by Slack next year.

my email: [email protected]

web site: jisrf.org

Regards,

Tim

Dear Timothy:

Sorry for the delay in answering but I was on the mountain with bad internet connection consequently cutting thereof according to the model used

My experience has been with two models :Fitmore and NiniHip. The indication we have made in people under 50 years with high level of physical activity, with a diagnosis of osteoarthritis or femoral head necrosis with preserved anatomy of the hip and low body mass index.

The approach always posterior and a high percentage MIS.It is very important the preservation of the femoral neck and correct cut, according to the model used

We employ the usual protocol :antibiotic prophylaxis and prevention of thromboembolism.

We maintain the patient with 2 crutches eight weeks with partial weight bearing .

I think it's an option in special cases, but I still think that an conventional anatomical coated with HA stem and C-C friction surfaces is an excellent indication in young people

Antonio,

I like that you added 2 crutches for eight weeks. I am concern especially with short stems. Physical activity today is higher than ever before. The current trend in the States is to issue no precautions. I think we put the reconstruction at risk by getting the patient too active  too quickly.

Timothy :

I agree , I  consider that is neccesary   to avoid the load to achieve a good secondary stability of stem

I also recommend 8 weeks partial weight bearing for cementless stems. I think full loading immediately postoperative to be risky. Some patients have thigh pain.Iate loading is reasonable.