Mrs Smith demanded to be told the qualifications of the service's prosthetic fitters and technicians in her search for answers, a quest that became a campaign to break the service's hold on state-paid limb-making. Alternative providers exist but have been hampered by the NZALS's dominance.
Now, after Mrs Smith's campaign, the Government is openly welcoming competition in the prosthetics market and says it will pay for amputees dissatisfied with the NZALS to be seen by other prosthetists.
Mrs Smith has revealed that the service was technically in breach of its funding agreement with the Accident Compensation Corporation and held contracts with overseas companies for the exclusive supply of parts for artificial limbs, which was a barrier to competitors. In refusing to accept second-best, Mrs Smith has cleared a path for other dissatisfied amputees to alternative providers.
The majority of the service's 4000 patients have had their treatment funded by the ACC, the rest by the public health system. Surveys indicate most are satisfied or very satisfied with the service, but about 160 are dissatisfied or very dissatisfied.
The ACC contract requires the service's staff to have specific qualifications, or appropriate experience and membership of the New Zealand Orthotics and Prosthetics Association, the NZOPA. Technicians must hold certificates of proficiency.
But a different group also exists, entirely within the NZALS. Most of its prosthetists and technicians nationally belong to this group, whose name at first glance seems similar: the Association of Orthopaedic Prosthetists, the NZAOP.
ACC spokeswoman Stephanie Melville said the service's staff "do not belong to the New Zealand Orthotics and Prosthetics Association as contractually required". ACC had reviewed the contract and investigated transtasman professional body requirements. It had issued a "breach notice" and would implement a performance improvement plan.
The service's chief executive, Sean Gray, dismissed criticism of his staff. In response to Mrs Smith's complaints, it hired Francis Group International consultancy, which confirmed the service's staff were appropriately skilled and qualified.
"NZALS is confident that our prosthetists and prosthetic technicians are appropriately qualified, competent and safe to deliver the services under the contract with ACC," Mr Gray said.
He acknowledged "historic anomalies in the contract", but would not comment on whether it had been breached. Its reference to the NZ Orthotics and Prosthetics Association was "a typographical error". This was supported by references to the correct organisation, the NZAOP, on the corporation's website, in earlier versions of the contract and in the service's contract with the Health Ministry.
Professional body membership is voluntary for prosthetists and technicians. The service's in-house association sets rules for members to gain proficiency and practising certificates. Minutes of the service's board meetings in 2013 record anxieties about the practising certificates of nine staff having expired.
After Mrs Smith complained to the Health and Disability Commissioner, an advocate persuaded the service it must tell her the qualifications of staff who worked on her prosthetics. Then-chief executive Mervyn Monk told her all were members of the in-house association and undertaking the required continuing professional development.
He said the technician who was a former Ministry of Works bulldozer operator and handyman "is himself an amputee and understands only too well the technical and prosthetics needs of most amputees".
Mrs Smith also received the practising certificates of some staff. One is for a technician who, as secretary of the association, is a signatory, along with the president, of her own certificate.
Mr Gray said self-signing was "not ideal" and without external regulation, it was important the service maintain close attention to quality assurance.
In 2012, board minutes voiced the need to foster the in-house association's development of competency assessment, to ensure it established "adequate and sustainable professional credentials".
Mr Gray said having two professional associations for prosthetics and orthotics was unusual and the two groups would merge.
When Mrs Smith lost confidence in the service and pushed ACC to pay for her to see a limb maker in Sydney, ACC suggested Wellington orthotics fitter Des Nicholson, who had also trained in prosthetics.
He found her existing fitting was too small and began making new prosthetics but at first couldn't get parts from overseas suppliers because of the NZALS's contracts.
Mrs Smith approached the Commerce Commission which she said told her it was giving the service three weeks to renegotiate the supply contracts.
The commission declined to comment to the Herald, other than to confirm it had received complaints.
The contracts with suppliers in Australia granted the service, as "sole provider of prosthetics", the "exclusive right" to sell the suppliers' products.
But Mr Gray said: "There was no intent for the NZALS to have an exclusive contract ... When this issue was raised, NZALS took appropriate actions, in good faith, to update these two supplier contracts to reflect the intent of non-exclusive."
ACC Minister Nikki Kaye said a wider inquiry into the matters raised by Mrs Smith was unnecessary as ACC and the service were committed to resolving the issues.
The Amputee Society of Auckland and Northland is staying out of Mrs Smith's dispute with the NZALS. Secretary Chris Ross said it provided a good service.
"There may be the odd case where it's not the best place for everyone to go; it's not one size fits all."
Limb maker improves lives of amputee clients
Artificial limb maker Des Nicholson is expanding his clinic after taking on dissatisfied amputee Diane Smith last year.
Since ACC referred her to him - after the New Zealand Artificial Limb Service (NZALS) was unable to make her an artificial leg that fitted properly - he has taken on seven more amputees.
This week, his Wellington clinic employed a third prosthetist/orthotist. It also has a student from Germany.
"There are other qualified orthotist/prosthetists that could also do prostheses if they are allowed to.
"If you have alternative suppliers it gives patients choices. Any other medical profession that you go to, you are entitled to a second opinion. In New Zealand if you wanted to go to a second prosthetist, where would you go?"
Mrs Smith and her amputee friend Jan Hansen, who also switched to Mr Nicholson, say their lives have changed immeasurably since he began making their legs.
Jan Hansen lost her right leg below the knee because of an infection contracted during surgery to remove pins and plates from her ankle.
The ankle had stabilised after a series of operations that began with repairs to fractures received when she slipped while gardening.
She said her prosthetics never fitted properly, causing excruciating lesions that required dressings on the stump - but that had all changed
"My grand-daughter said, 'I have never seen you walking so well'. I just felt like, my God, I can walk."
Mrs Smith said she can now use her prosthetics all day, whereas she could cope with the NZALS legs for only short periods, before the pain got too much. "I'm able to get around, I'm feeling much better, I have got more energy, just doing things that I haven't done in years, like cooking. I haven't used crutches since last September and I used them all the time with the NZALS because I couldn't walk."
She is regaining independence and is starting to imagine a return to work, in a field in which she has become an expert: "I want to be an advocate and support person for amputees."
